<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2023 Workiva-->
<!--r:5cb8ff8a-ed58-4b5c-b8ff-c77a2229ab62,g:17d364b7-1fd4-44c1-a87d-98f3b18d5a50-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.intlfcstone.com/role/CondensedConsolidatedIncomeStatements" xlink:type="simple" xlink:href="intl-20230630.xsd#CondensedConsolidatedIncomeStatements"/>
  <link:definitionLink xlink:role="http://www.intlfcstone.com/role/CondensedConsolidatedIncomeStatements" xlink:type="extended" id="i8cee1196285a4de09b1041dc0fabfe4f_CondensedConsolidatedIncomeStatements">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_15c9cbf9-e107-4631-aa78-f27c4f5244c9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesAbstract_d6526499-a8cb-461c-869d-d8228001020f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenuesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_15c9cbf9-e107-4631-aa78-f27c4f5244c9" xlink:to="loc_us-gaap_RevenuesAbstract_d6526499-a8cb-461c-869d-d8228001020f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_a967c792-1bd6-4ae5-8e1a-5f22f6a366b2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_d6526499-a8cb-461c-869d-d8228001020f" xlink:to="loc_us-gaap_Revenues_a967c792-1bd6-4ae5-8e1a-5f22f6a366b2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServiceExcludingDepreciationDepletionAndAmortization_b5424436-62f8-4c54-b98b-a20798a86584" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CostOfGoodsAndServiceExcludingDepreciationDepletionAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_d6526499-a8cb-461c-869d-d8228001020f" xlink:to="loc_us-gaap_CostOfGoodsAndServiceExcludingDepreciationDepletionAndAmortization_b5424436-62f8-4c54-b98b-a20798a86584" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossProfit_e2cd179a-243d-43c0-8b53-7a6be1850cf3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GrossProfit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_d6526499-a8cb-461c-869d-d8228001020f" xlink:to="loc_us-gaap_GrossProfit_e2cd179a-243d-43c0-8b53-7a6be1850cf3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FloorBrokerageExchangeAndClearanceFees_8de9af00-1170-4d02-9816-95587392bfdc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FloorBrokerageExchangeAndClearanceFees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_d6526499-a8cb-461c-869d-d8228001020f" xlink:to="loc_us-gaap_FloorBrokerageExchangeAndClearanceFees_8de9af00-1170-4d02-9816-95587392bfdc" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoninterestExpenseCommissionExpense_5d78c2a5-74dd-4fe0-a915-39e6612e054f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NoninterestExpenseCommissionExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_d6526499-a8cb-461c-869d-d8228001020f" xlink:to="loc_us-gaap_NoninterestExpenseCommissionExpense_5d78c2a5-74dd-4fe0-a915-39e6612e054f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense_64ea7ddf-3f73-4b08-b1b4-ea92148c1402" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_d6526499-a8cb-461c-869d-d8228001020f" xlink:to="loc_us-gaap_InterestExpense_64ea7ddf-3f73-4b08-b1b4-ea92148c1402" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_InterestExpenseOnCorporateFunding_24ed12d2-d8e2-4a6c-8139-3fb068ebb1af" xlink:href="intl-20230630.xsd#intl_InterestExpenseOnCorporateFunding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_d6526499-a8cb-461c-869d-d8228001020f" xlink:to="loc_intl_InterestExpenseOnCorporateFunding_24ed12d2-d8e2-4a6c-8139-3fb068ebb1af" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesNetOfInterestExpense_54718ade-694b-4c03-a448-a01b10b9ad24" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenuesNetOfInterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_d6526499-a8cb-461c-869d-d8228001020f" xlink:to="loc_us-gaap_RevenuesNetOfInterestExpense_54718ade-694b-4c03-a448-a01b10b9ad24" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoninterestExpenseAbstract_a767595f-3aa5-4b41-b128-0b987b9656e0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NoninterestExpenseAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_d6526499-a8cb-461c-869d-d8228001020f" xlink:to="loc_us-gaap_NoninterestExpenseAbstract_a767595f-3aa5-4b41-b128-0b987b9656e0" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LaborAndRelatedExpense_f49eda2c-9654-4156-98a1-f49230cc0899" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LaborAndRelatedExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoninterestExpenseAbstract_a767595f-3aa5-4b41-b128-0b987b9656e0" xlink:to="loc_us-gaap_LaborAndRelatedExpense_f49eda2c-9654-4156-98a1-f49230cc0899" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_Tradingsystemsandmarketinformation_378a2e2d-1627-41fd-aa14-c20d8152fb78" xlink:href="intl-20230630.xsd#intl_Tradingsystemsandmarketinformation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoninterestExpenseAbstract_a767595f-3aa5-4b41-b128-0b987b9656e0" xlink:to="loc_intl_Tradingsystemsandmarketinformation_378a2e2d-1627-41fd-aa14-c20d8152fb78" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfessionalFees_555b58d1-337a-4479-b6eb-a3ac79e7a23e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProfessionalFees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoninterestExpenseAbstract_a767595f-3aa5-4b41-b128-0b987b9656e0" xlink:to="loc_us-gaap_ProfessionalFees_555b58d1-337a-4479-b6eb-a3ac79e7a23e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InformationTechnologyAndDataProcessing_b451f28e-f68a-4e88-b5dc-6954c949fc21" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InformationTechnologyAndDataProcessing"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoninterestExpenseAbstract_a767595f-3aa5-4b41-b128-0b987b9656e0" xlink:to="loc_us-gaap_InformationTechnologyAndDataProcessing_b451f28e-f68a-4e88-b5dc-6954c949fc21" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OccupancyNet_e6f0f704-ef02-447f-beb2-c4cad983ca4b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OccupancyNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoninterestExpenseAbstract_a767595f-3aa5-4b41-b128-0b987b9656e0" xlink:to="loc_us-gaap_OccupancyNet_e6f0f704-ef02-447f-beb2-c4cad983ca4b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingAndMarketingExpense_83a7e61e-2235-4fec-b494-9b0ef7973c5e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SellingAndMarketingExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoninterestExpenseAbstract_a767595f-3aa5-4b41-b128-0b987b9656e0" xlink:to="loc_us-gaap_SellingAndMarketingExpense_83a7e61e-2235-4fec-b494-9b0ef7973c5e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TravelAndEntertainmentExpense_cbd23805-f735-49b6-8ec6-9dce26d45d1a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TravelAndEntertainmentExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoninterestExpenseAbstract_a767595f-3aa5-4b41-b128-0b987b9656e0" xlink:to="loc_us-gaap_TravelAndEntertainmentExpense_cbd23805-f735-49b6-8ec6-9dce26d45d1a" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Communication_24b006a0-b828-4fb8-835b-71bc54e6f8c9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Communication"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoninterestExpenseAbstract_a767595f-3aa5-4b41-b128-0b987b9656e0" xlink:to="loc_us-gaap_Communication_24b006a0-b828-4fb8-835b-71bc54e6f8c9" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_265de80b-efe8-4a4f-981e-4525016932dc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoninterestExpenseAbstract_a767595f-3aa5-4b41-b128-0b987b9656e0" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_265de80b-efe8-4a4f-981e-4525016932dc" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProvisionForDoubtfulAccounts_521b82f9-9657-4024-8297-bcfd97cc9b76" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProvisionForDoubtfulAccounts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoninterestExpenseAbstract_a767595f-3aa5-4b41-b128-0b987b9656e0" xlink:to="loc_us-gaap_ProvisionForDoubtfulAccounts_521b82f9-9657-4024-8297-bcfd97cc9b76" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNoninterestExpense_80ab0d90-c976-490a-9e40-a52a4cd2a29b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherNoninterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoninterestExpenseAbstract_a767595f-3aa5-4b41-b128-0b987b9656e0" xlink:to="loc_us-gaap_OtherNoninterestExpense_80ab0d90-c976-490a-9e40-a52a4cd2a29b" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoninterestExpense_eb8c21a9-2abf-4a4a-ab26-9d1f0ee4dceb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NoninterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoninterestExpenseAbstract_a767595f-3aa5-4b41-b128-0b987b9656e0" xlink:to="loc_us-gaap_NoninterestExpense_eb8c21a9-2abf-4a4a-ab26-9d1f0ee4dceb" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_GainLossOnAcquisitionsAndOther_6b22b478-0e2f-4910-9b3b-efc12bbd6408" xlink:href="intl-20230630.xsd#intl_GainLossOnAcquisitionsAndOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_d6526499-a8cb-461c-869d-d8228001020f" xlink:to="loc_intl_GainLossOnAcquisitionsAndOther_6b22b478-0e2f-4910-9b3b-efc12bbd6408" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_702b5e43-248a-4e50-b78c-f3d3cde0cc00" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_d6526499-a8cb-461c-869d-d8228001020f" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_702b5e43-248a-4e50-b78c-f3d3cde0cc00" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_d44cc266-46f9-441c-bb69-9bcdc53b31ed" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_d6526499-a8cb-461c-869d-d8228001020f" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_d44cc266-46f9-441c-bb69-9bcdc53b31ed" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_5ee7e2e2-7def-4b1b-8fad-a36b42a3864c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_d6526499-a8cb-461c-869d-d8228001020f" xlink:to="loc_us-gaap_NetIncomeLoss_5ee7e2e2-7def-4b1b-8fad-a36b42a3864c" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasicAbstract_17bf8b03-c6bd-46af-9f7a-553348dec86c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareBasicAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_d6526499-a8cb-461c-869d-d8228001020f" xlink:to="loc_us-gaap_EarningsPerShareBasicAbstract_17bf8b03-c6bd-46af-9f7a-553348dec86c" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_d79d9f4e-ca0d-4e83-b203-e46ad9277c39" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_17bf8b03-c6bd-46af-9f7a-553348dec86c" xlink:to="loc_us-gaap_EarningsPerShareBasic_d79d9f4e-ca0d-4e83-b203-e46ad9277c39" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_bf908394-bf97-4110-87d6-73447a4f2912" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_17bf8b03-c6bd-46af-9f7a-553348dec86c" xlink:to="loc_us-gaap_EarningsPerShareDiluted_bf908394-bf97-4110-87d6-73447a4f2912" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_267c74fa-316d-404e-b736-aea7340cde12" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_d6526499-a8cb-461c-869d-d8228001020f" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_267c74fa-316d-404e-b736-aea7340cde12" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_7e3d385a-62dc-46b6-8891-cae6a9a6e737" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_267c74fa-316d-404e-b736-aea7340cde12" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_7e3d385a-62dc-46b6-8891-cae6a9a6e737" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_ed34c268-d60a-416b-8f39-91eba5fdcbf2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_267c74fa-316d-404e-b736-aea7340cde12" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_ed34c268-d60a-416b-8f39-91eba5fdcbf2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_9773e02a-fcfc-406f-b789-451e2e3276cd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_15c9cbf9-e107-4631-aa78-f27c4f5244c9" xlink:to="loc_us-gaap_StatementTable_9773e02a-fcfc-406f-b789-451e2e3276cd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_d7eabeee-3156-45a7-9b41-5259a1a70f8e" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_9773e02a-fcfc-406f-b789-451e2e3276cd" xlink:to="loc_srt_ProductOrServiceAxis_d7eabeee-3156-45a7-9b41-5259a1a70f8e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_d7eabeee-3156-45a7-9b41-5259a1a70f8e_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_d7eabeee-3156-45a7-9b41-5259a1a70f8e" xlink:to="loc_srt_ProductsAndServicesDomain_d7eabeee-3156-45a7-9b41-5259a1a70f8e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_203e379e-a27c-441b-a0ac-37dcfcd39ef8" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_d7eabeee-3156-45a7-9b41-5259a1a70f8e" xlink:to="loc_srt_ProductsAndServicesDomain_203e379e-a27c-441b-a0ac-37dcfcd39ef8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_SalesOfPhysicalCommoditiesMember_213cf992-96b4-4d80-aae3-6d513ac2fac9" xlink:href="intl-20230630.xsd#intl_SalesOfPhysicalCommoditiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_203e379e-a27c-441b-a0ac-37dcfcd39ef8" xlink:to="loc_intl_SalesOfPhysicalCommoditiesMember_213cf992-96b4-4d80-aae3-6d513ac2fac9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_PrincipalGainsNetMember_e9b1af3b-c278-4d04-b585-113c2e03cecc" xlink:href="intl-20230630.xsd#intl_PrincipalGainsNetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_203e379e-a27c-441b-a0ac-37dcfcd39ef8" xlink:to="loc_intl_PrincipalGainsNetMember_e9b1af3b-c278-4d04-b585-113c2e03cecc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_CommissionandClearingFeesMember_2c14f170-d0dc-40a4-847a-886daf4a892e" xlink:href="intl-20230630.xsd#intl_CommissionandClearingFeesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_203e379e-a27c-441b-a0ac-37dcfcd39ef8" xlink:to="loc_intl_CommissionandClearingFeesMember_2c14f170-d0dc-40a4-847a-886daf4a892e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_ConsultingManagementAndAccountFeesMember_5d951c27-2489-405a-a6bb-4a4896040efc" xlink:href="intl-20230630.xsd#intl_ConsultingManagementAndAccountFeesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_203e379e-a27c-441b-a0ac-37dcfcd39ef8" xlink:to="loc_intl_ConsultingManagementAndAccountFeesMember_5d951c27-2489-405a-a6bb-4a4896040efc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_InterestIncomeNetMember_2bd284ae-a129-4d17-a42a-9812274961ad" xlink:href="intl-20230630.xsd#intl_InterestIncomeNetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_203e379e-a27c-441b-a0ac-37dcfcd39ef8" xlink:to="loc_intl_InterestIncomeNetMember_2bd284ae-a129-4d17-a42a-9812274961ad" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.intlfcstone.com/role/CondensedConsolidatedStatementsofStockholdersEquity" xlink:type="simple" xlink:href="intl-20230630.xsd#CondensedConsolidatedStatementsofStockholdersEquity"/>
  <link:definitionLink xlink:role="http://www.intlfcstone.com/role/CondensedConsolidatedStatementsofStockholdersEquity" xlink:type="extended" id="id1c54adde78b4d98980b8c9b7d35791d_CondensedConsolidatedStatementsofStockholdersEquity">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_a367a72b-39bf-407c-ac87-6fd473f2a634" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_9cf0a2af-aec6-4374-8a4f-6847affcfa64" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_a367a72b-39bf-407c-ac87-6fd473f2a634" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_9cf0a2af-aec6-4374-8a4f-6847affcfa64" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_7f02c4d3-bf25-41e8-a358-edaeed42f79f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_9cf0a2af-aec6-4374-8a4f-6847affcfa64" xlink:to="loc_us-gaap_StockholdersEquity_7f02c4d3-bf25-41e8-a358-edaeed42f79f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_39579990-6283-4c3d-a18d-55da4376bc07" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_9cf0a2af-aec6-4374-8a4f-6847affcfa64" xlink:to="loc_us-gaap_NetIncomeLoss_39579990-6283-4c3d-a18d-55da4376bc07" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_f51a3398-5003-41c7-88d9-607d66d5c76b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_9cf0a2af-aec6-4374-8a4f-6847affcfa64" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_f51a3398-5003-41c7-88d9-607d66d5c76b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_d2a44bd0-7d23-4604-a47d-a9fe93091ab7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_9cf0a2af-aec6-4374-8a4f-6847affcfa64" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_d2a44bd0-7d23-4604-a47d-a9fe93091ab7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_fe27c4c7-ff05-489a-bef8-ea53e25a5687" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_9cf0a2af-aec6-4374-8a4f-6847affcfa64" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_fe27c4c7-ff05-489a-bef8-ea53e25a5687" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_ab7edc0f-8c03-4c54-915e-d76476256920" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_17ab8a80-7251-4e66-ad19-d17236751ed9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_a367a72b-39bf-407c-ac87-6fd473f2a634" xlink:to="loc_us-gaap_StatementTable_17ab8a80-7251-4e66-ad19-d17236751ed9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_e590d4a4-9ff5-4f0a-91a8-6e12854e55a7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_17ab8a80-7251-4e66-ad19-d17236751ed9" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_e590d4a4-9ff5-4f0a-91a8-6e12854e55a7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_e590d4a4-9ff5-4f0a-91a8-6e12854e55a7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_e590d4a4-9ff5-4f0a-91a8-6e12854e55a7" xlink:to="loc_us-gaap_EquityComponentDomain_e590d4a4-9ff5-4f0a-91a8-6e12854e55a7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_8a005b5e-eba8-42c7-bb4a-aaa867ff048f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_e590d4a4-9ff5-4f0a-91a8-6e12854e55a7" xlink:to="loc_us-gaap_EquityComponentDomain_8a005b5e-eba8-42c7-bb4a-aaa867ff048f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_63d5d2a0-3d08-4087-9adb-b598c0b94881" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_8a005b5e-eba8-42c7-bb4a-aaa867ff048f" xlink:to="loc_us-gaap_CommonStockMember_63d5d2a0-3d08-4087-9adb-b598c0b94881" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonMember_37339c0f-7396-46ba-9942-60e0b00b5c90" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TreasuryStockCommonMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_8a005b5e-eba8-42c7-bb4a-aaa867ff048f" xlink:to="loc_us-gaap_TreasuryStockCommonMember_37339c0f-7396-46ba-9942-60e0b00b5c90" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_77a6836d-07fd-4234-a640-827c1f60e353" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_8a005b5e-eba8-42c7-bb4a-aaa867ff048f" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_77a6836d-07fd-4234-a640-827c1f60e353" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_4cee0798-0779-4215-a9be-64f901163e02" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_8a005b5e-eba8-42c7-bb4a-aaa867ff048f" xlink:to="loc_us-gaap_RetainedEarningsMember_4cee0798-0779-4215-a9be-64f901163e02" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_1493ccb5-2d60-485a-ae89-4426d91ab249" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_8a005b5e-eba8-42c7-bb4a-aaa867ff048f" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_1493ccb5-2d60-485a-ae89-4426d91ab249" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.intlfcstone.com/role/BasisofPresentationandConsolidationandAccountingStandardsAdoptedDetails" xlink:type="simple" xlink:href="intl-20230630.xsd#BasisofPresentationandConsolidationandAccountingStandardsAdoptedDetails"/>
  <link:definitionLink xlink:role="http://www.intlfcstone.com/role/BasisofPresentationandConsolidationandAccountingStandardsAdoptedDetails" xlink:type="extended" id="i743dad16cd1842daa3a5398d0a033d44_BasisofPresentationandConsolidationandAccountingStandardsAdoptedDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_550b404a-863a-45f5-88b4-12590f007f49" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfCountriesInWhichEntityOperates_e4aef63b-2208-4009-b5dd-2c23e5a9f0b7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NumberOfCountriesInWhichEntityOperates"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_550b404a-863a-45f5-88b4-12590f007f49" xlink:to="loc_us-gaap_NumberOfCountriesInWhichEntityOperates_e4aef63b-2208-4009-b5dd-2c23e5a9f0b7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_NumberOfCommercialAndInstitutionalClients_73f391f7-1fe1-463c-95f9-a54235f2dbb2" xlink:href="intl-20230630.xsd#intl_NumberOfCommercialAndInstitutionalClients"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_550b404a-863a-45f5-88b4-12590f007f49" xlink:to="loc_intl_NumberOfCommercialAndInstitutionalClients_73f391f7-1fe1-463c-95f9-a54235f2dbb2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_NumberRetailClients_9db583a0-0764-4faa-8a91-65dd7207eeeb" xlink:href="intl-20230630.xsd#intl_NumberRetailClients"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_550b404a-863a-45f5-88b4-12590f007f49" xlink:to="loc_intl_NumberRetailClients_9db583a0-0764-4faa-8a91-65dd7207eeeb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_2915d9a8-361f-4ee4-9f6b-f4d40bb41cd6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_550b404a-863a-45f5-88b4-12590f007f49" xlink:to="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_2915d9a8-361f-4ee4-9f6b-f4d40bb41cd6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_14c332db-625d-402f-826f-0d5826a6d011" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_2915d9a8-361f-4ee4-9f6b-f4d40bb41cd6" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_14c332db-625d-402f-826f-0d5826a6d011" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_14c332db-625d-402f-826f-0d5826a6d011_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_14c332db-625d-402f-826f-0d5826a6d011" xlink:to="loc_us-gaap_SegmentDomain_14c332db-625d-402f-826f-0d5826a6d011_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_b744c74c-eef3-4d2e-bd8d-f8eb88b5ceca" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_14c332db-625d-402f-826f-0d5826a6d011" xlink:to="loc_us-gaap_SegmentDomain_b744c74c-eef3-4d2e-bd8d-f8eb88b5ceca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_RetailSegmentMember_79641b9c-faa3-4559-87e1-7740dd37da14" xlink:href="intl-20230630.xsd#intl_RetailSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_b744c74c-eef3-4d2e-bd8d-f8eb88b5ceca" xlink:to="loc_intl_RetailSegmentMember_79641b9c-faa3-4559-87e1-7740dd37da14" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.intlfcstone.com/role/AssetsandLiabilitiesatFairValueNarrativeDetails" xlink:type="simple" xlink:href="intl-20230630.xsd#AssetsandLiabilitiesatFairValueNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.intlfcstone.com/role/AssetsandLiabilitiesatFairValueNarrativeDetails" xlink:type="extended" id="i6ef78ea8a13047f390be1c308567d962_AssetsandLiabilitiesatFairValueNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7a23e6f9-e5e0-4b1d-9693-127572c473b2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableAndOtherAccruedLiabilities_69cdd9b2-9406-4ae5-9f1a-15ca44a03d89" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsPayableAndOtherAccruedLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7a23e6f9-e5e0-4b1d-9693-127572c473b2" xlink:to="loc_us-gaap_AccountsPayableAndOtherAccruedLiabilities_69cdd9b2-9406-4ae5-9f1a-15ca44a03d89" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_e3618ade-e920-4f7c-89f1-974d9b14634c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7a23e6f9-e5e0-4b1d-9693-127572c473b2" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_e3618ade-e920-4f7c-89f1-974d9b14634c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotes_e18596a2-2548-4f59-baa6-40a9fe5991a8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SeniorNotes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7a23e6f9-e5e0-4b1d-9693-127572c473b2" xlink:to="loc_us-gaap_SeniorNotes_e18596a2-2548-4f59-baa6-40a9fe5991a8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtFairValue_cab146e4-0044-4fb7-a19c-5de87c3cf21f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7a23e6f9-e5e0-4b1d-9693-127572c473b2" xlink:to="loc_us-gaap_LongTermDebtFairValue_cab146e4-0044-4fb7-a19c-5de87c3cf21f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_6b99b1e3-69e8-454d-a3bf-1d912a02a21d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7a23e6f9-e5e0-4b1d-9693-127572c473b2" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_6b99b1e3-69e8-454d-a3bf-1d912a02a21d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_AccountsPayableAndOtherAccruedLiabilitiesIncludingContingentLiabilitiesAxis_04df3958-e42c-4b78-bf5c-cb64ff413ac8" xlink:href="intl-20230630.xsd#intl_AccountsPayableAndOtherAccruedLiabilitiesIncludingContingentLiabilitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_6b99b1e3-69e8-454d-a3bf-1d912a02a21d" xlink:to="loc_intl_AccountsPayableAndOtherAccruedLiabilitiesIncludingContingentLiabilitiesAxis_04df3958-e42c-4b78-bf5c-cb64ff413ac8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_AccountsPayableAndOtherAccruedLiabilitiesIncludingContingentLiabilitiesDomain_04df3958-e42c-4b78-bf5c-cb64ff413ac8_default" xlink:href="intl-20230630.xsd#intl_AccountsPayableAndOtherAccruedLiabilitiesIncludingContingentLiabilitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_intl_AccountsPayableAndOtherAccruedLiabilitiesIncludingContingentLiabilitiesAxis_04df3958-e42c-4b78-bf5c-cb64ff413ac8" xlink:to="loc_intl_AccountsPayableAndOtherAccruedLiabilitiesIncludingContingentLiabilitiesDomain_04df3958-e42c-4b78-bf5c-cb64ff413ac8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_AccountsPayableAndOtherAccruedLiabilitiesIncludingContingentLiabilitiesDomain_3414537d-a318-4706-b716-187d2d65eb63" xlink:href="intl-20230630.xsd#intl_AccountsPayableAndOtherAccruedLiabilitiesIncludingContingentLiabilitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_intl_AccountsPayableAndOtherAccruedLiabilitiesIncludingContingentLiabilitiesAxis_04df3958-e42c-4b78-bf5c-cb64ff413ac8" xlink:to="loc_intl_AccountsPayableAndOtherAccruedLiabilitiesIncludingContingentLiabilitiesDomain_3414537d-a318-4706-b716-187d2d65eb63" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_ContingentConsiderationMember_502e83dc-979e-49f5-89a4-8ba14cae3501" xlink:href="intl-20230630.xsd#intl_ContingentConsiderationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_intl_AccountsPayableAndOtherAccruedLiabilitiesIncludingContingentLiabilitiesDomain_3414537d-a318-4706-b716-187d2d65eb63" xlink:to="loc_intl_ContingentConsiderationMember_502e83dc-979e-49f5-89a4-8ba14cae3501" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_007fe18a-3a17-448b-85a8-8f0ea608b8e7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_6b99b1e3-69e8-454d-a3bf-1d912a02a21d" xlink:to="loc_us-gaap_DebtInstrumentAxis_007fe18a-3a17-448b-85a8-8f0ea608b8e7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_007fe18a-3a17-448b-85a8-8f0ea608b8e7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_007fe18a-3a17-448b-85a8-8f0ea608b8e7" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_007fe18a-3a17-448b-85a8-8f0ea608b8e7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_29a54ef8-9976-4644-902f-417f32e5ee39" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_007fe18a-3a17-448b-85a8-8f0ea608b8e7" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_29a54ef8-9976-4644-902f-417f32e5ee39" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_SeniorNotesDueTwentyTwentyFiveMember_1d48d65d-72f9-44f7-aef2-139b77120bc3" xlink:href="intl-20230630.xsd#intl_SeniorNotesDueTwentyTwentyFiveMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_29a54ef8-9976-4644-902f-417f32e5ee39" xlink:to="loc_intl_SeniorNotesDueTwentyTwentyFiveMember_1d48d65d-72f9-44f7-aef2-139b77120bc3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_0aef5d4d-e01d-4fcf-8891-9f3fa90a087a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_6b99b1e3-69e8-454d-a3bf-1d912a02a21d" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_0aef5d4d-e01d-4fcf-8891-9f3fa90a087a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_0aef5d4d-e01d-4fcf-8891-9f3fa90a087a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_0aef5d4d-e01d-4fcf-8891-9f3fa90a087a" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_0aef5d4d-e01d-4fcf-8891-9f3fa90a087a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_4a66d66e-66d4-4414-b61a-ba797045260d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_0aef5d4d-e01d-4fcf-8891-9f3fa90a087a" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_4a66d66e-66d4-4414-b61a-ba797045260d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_ec0f4883-1803-4ac9-9c83-020ec180badc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_4a66d66e-66d4-4414-b61a-ba797045260d" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_ec0f4883-1803-4ac9-9c83-020ec180badc" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.intlfcstone.com/role/AssetsandLiabilitiesatFairValueFinancialAssetsandLiabilitiesMeasuredatFairValueDetails" xlink:type="simple" xlink:href="intl-20230630.xsd#AssetsandLiabilitiesatFairValueFinancialAssetsandLiabilitiesMeasuredatFairValueDetails"/>
  <link:definitionLink xlink:role="http://www.intlfcstone.com/role/AssetsandLiabilitiesatFairValueFinancialAssetsandLiabilitiesMeasuredatFairValueDetails" xlink:type="extended" id="i0656edfd50924489a5de6b7f44da2b9a_AssetsandLiabilitiesatFairValueFinancialAssetsandLiabilitiesMeasuredatFairValueDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_a97386c2-f572-40fc-aff7-3d32e771f262" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Cash_5086c5ba-2769-45be-b15d-0d2b1e889167" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Cash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_a97386c2-f572-40fc-aff7-3d32e771f262" xlink:to="loc_us-gaap_Cash_5086c5ba-2769-45be-b15d-0d2b1e889167" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_9f1f4003-0647-4aa3-ba3f-2828ebd5a04e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_a97386c2-f572-40fc-aff7-3d32e771f262" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_9f1f4003-0647-4aa3-ba3f-2828ebd5a04e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndSecuritiesSegregatedUnderFederalAndOtherRegulations_ceb65308-b645-4b59-ac8b-f6d9eb2180dd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashAndSecuritiesSegregatedUnderFederalAndOtherRegulations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_a97386c2-f572-40fc-aff7-3d32e771f262" xlink:to="loc_us-gaap_CashAndSecuritiesSegregatedUnderFederalAndOtherRegulations_ceb65308-b645-4b59-ac8b-f6d9eb2180dd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_ReceivablesFromClearingOrganizationsIncludingNettingAdjustment_28d71577-e2c0-4dea-af74-7ba598ec154e" xlink:href="intl-20230630.xsd#intl_ReceivablesFromClearingOrganizationsIncludingNettingAdjustment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_a97386c2-f572-40fc-aff7-3d32e771f262" xlink:to="loc_intl_ReceivablesFromClearingOrganizationsIncludingNettingAdjustment_28d71577-e2c0-4dea-af74-7ba598ec154e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_AccountsReceivableIncludingNettingAdjustmentFairValueDisclosure_5d611677-9a0c-40cd-bcb1-7edd2462b50a" xlink:href="intl-20230630.xsd#intl_AccountsReceivableIncludingNettingAdjustmentFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_a97386c2-f572-40fc-aff7-3d32e771f262" xlink:to="loc_intl_AccountsReceivableIncludingNettingAdjustmentFairValueDisclosure_5d611677-9a0c-40cd-bcb1-7edd2462b50a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentsOwnedAtFairValue_3d99679b-66df-4abb-a89b-926948101ffe" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentsOwnedAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_a97386c2-f572-40fc-aff7-3d32e771f262" xlink:to="loc_us-gaap_FinancialInstrumentsOwnedAtFairValue_3d99679b-66df-4abb-a89b-926948101ffe" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryGross_af78561b-0b10-4717-ba97-b1cc214bf904" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InventoryGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_a97386c2-f572-40fc-aff7-3d32e771f262" xlink:to="loc_us-gaap_InventoryGross_af78561b-0b10-4717-ba97-b1cc214bf904" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_fc752852-c7c6-428d-a91a-5b2b8a7bf70e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_a97386c2-f572-40fc-aff7-3d32e771f262" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_fc752852-c7c6-428d-a91a-5b2b8a7bf70e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableAndOtherAccruedLiabilities_c59e08b6-4dda-4714-b4fa-5b061c88643b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsPayableAndOtherAccruedLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_a97386c2-f572-40fc-aff7-3d32e771f262" xlink:to="loc_us-gaap_AccountsPayableAndOtherAccruedLiabilities_c59e08b6-4dda-4714-b4fa-5b061c88643b" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_AccountsPayableIncludingNettingAdjustmentFairValueDisclosure_b5e06e77-236e-48ee-972f-2f2af686122e" xlink:href="intl-20230630.xsd#intl_AccountsPayableIncludingNettingAdjustmentFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_a97386c2-f572-40fc-aff7-3d32e771f262" xlink:to="loc_intl_AccountsPayableIncludingNettingAdjustmentFairValueDisclosure_b5e06e77-236e-48ee-972f-2f2af686122e" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_BrokerDealerPayableToOtherBrokerDealerAndClearingOrganizationIncludingNettingAdjustment_29e1b9f6-5322-4ac6-9d02-dd818eda39f4" xlink:href="intl-20230630.xsd#intl_BrokerDealerPayableToOtherBrokerDealerAndClearingOrganizationIncludingNettingAdjustment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_a97386c2-f572-40fc-aff7-3d32e771f262" xlink:to="loc_intl_BrokerDealerPayableToOtherBrokerDealerAndClearingOrganizationIncludingNettingAdjustment_29e1b9f6-5322-4ac6-9d02-dd818eda39f4" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentsSoldNotYetPurchasedAtFairValue_dd36de7f-0752-44d2-a262-8b6565fbc6f4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentsSoldNotYetPurchasedAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_a97386c2-f572-40fc-aff7-3d32e771f262" xlink:to="loc_us-gaap_FinancialInstrumentsSoldNotYetPurchasedAtFairValue_dd36de7f-0752-44d2-a262-8b6565fbc6f4" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosure_cd35bf3c-8e3a-4e46-ac16-ab846668f063" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_a97386c2-f572-40fc-aff7-3d32e771f262" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosure_cd35bf3c-8e3a-4e46-ac16-ab846668f063" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_b0994aa8-a087-419a-a92e-5ccc19c12abf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_a97386c2-f572-40fc-aff7-3d32e771f262" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_b0994aa8-a087-419a-a92e-5ccc19c12abf" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_afda7653-4291-4901-89e6-b884f6053449" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_b0994aa8-a087-419a-a92e-5ccc19c12abf" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_afda7653-4291-4901-89e6-b884f6053449" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_afda7653-4291-4901-89e6-b884f6053449_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_afda7653-4291-4901-89e6-b884f6053449" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_afda7653-4291-4901-89e6-b884f6053449_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_bffa62ba-9824-4e80-b3b9-d9e58a04ef7a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_afda7653-4291-4901-89e6-b884f6053449" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_bffa62ba-9824-4e80-b3b9-d9e58a04ef7a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_5834c7cc-26e8-41cf-9e86-c3b463581cf4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_bffa62ba-9824-4e80-b3b9-d9e58a04ef7a" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_5834c7cc-26e8-41cf-9e86-c3b463581cf4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_4e18ca63-5bdb-4105-abe3-dc2a03672cd4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_b0994aa8-a087-419a-a92e-5ccc19c12abf" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_4e18ca63-5bdb-4105-abe3-dc2a03672cd4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_4e18ca63-5bdb-4105-abe3-dc2a03672cd4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_4e18ca63-5bdb-4105-abe3-dc2a03672cd4" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_4e18ca63-5bdb-4105-abe3-dc2a03672cd4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_49ce545b-dfa1-47b7-8d1b-1819930be913" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_4e18ca63-5bdb-4105-abe3-dc2a03672cd4" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_49ce545b-dfa1-47b7-8d1b-1819930be913" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_a2ebc04d-4575-4ba0-8620-4b112b2536e2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_49ce545b-dfa1-47b7-8d1b-1819930be913" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_a2ebc04d-4575-4ba0-8620-4b112b2536e2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_2ceb0d78-1691-4abb-8d23-de70de3bcde3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_49ce545b-dfa1-47b7-8d1b-1819930be913" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_2ceb0d78-1691-4abb-8d23-de70de3bcde3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_faa20e7d-f13a-4592-9c21-9bb2b14889fc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_49ce545b-dfa1-47b7-8d1b-1819930be913" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_faa20e7d-f13a-4592-9c21-9bb2b14889fc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_DerivativeNettingAdjustmentAxis_80b6f2b8-9a57-41fa-a058-c031ed79de16" xlink:href="intl-20230630.xsd#intl_DerivativeNettingAdjustmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_b0994aa8-a087-419a-a92e-5ccc19c12abf" xlink:to="loc_intl_DerivativeNettingAdjustmentAxis_80b6f2b8-9a57-41fa-a058-c031ed79de16" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_DerivativeNettingAdjustmentDomain_80b6f2b8-9a57-41fa-a058-c031ed79de16_default" xlink:href="intl-20230630.xsd#intl_DerivativeNettingAdjustmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_intl_DerivativeNettingAdjustmentAxis_80b6f2b8-9a57-41fa-a058-c031ed79de16" xlink:to="loc_intl_DerivativeNettingAdjustmentDomain_80b6f2b8-9a57-41fa-a058-c031ed79de16_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_DerivativeNettingAdjustmentDomain_b557b1b4-b5dd-4404-9d67-9dfc894a2907" xlink:href="intl-20230630.xsd#intl_DerivativeNettingAdjustmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_intl_DerivativeNettingAdjustmentAxis_80b6f2b8-9a57-41fa-a058-c031ed79de16" xlink:to="loc_intl_DerivativeNettingAdjustmentDomain_b557b1b4-b5dd-4404-9d67-9dfc894a2907" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_CounterpartyAndCashCollateralNettingAdjustmentMember_cf96696b-2f43-4f5d-86e5-08c1ed99989c" xlink:href="intl-20230630.xsd#intl_CounterpartyAndCashCollateralNettingAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_intl_DerivativeNettingAdjustmentDomain_b557b1b4-b5dd-4404-9d67-9dfc894a2907" xlink:to="loc_intl_CounterpartyAndCashCollateralNettingAdjustmentMember_cf96696b-2f43-4f5d-86e5-08c1ed99989c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAxis_f1340319-22dc-4eb7-a213-7b6ef70eed83" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashAndCashEquivalentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_b0994aa8-a087-419a-a92e-5ccc19c12abf" xlink:to="loc_us-gaap_CashAndCashEquivalentsAxis_f1340319-22dc-4eb7-a213-7b6ef70eed83" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_f1340319-22dc-4eb7-a213-7b6ef70eed83_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_f1340319-22dc-4eb7-a213-7b6ef70eed83" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_f1340319-22dc-4eb7-a213-7b6ef70eed83_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_0a8d6ecb-5c42-45b4-996e-e33b914922c9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_f1340319-22dc-4eb7-a213-7b6ef70eed83" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_0a8d6ecb-5c42-45b4-996e-e33b914922c9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CertificatesOfDepositMember_a10f706c-a457-4644-94be-fa097d63f16e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CertificatesOfDepositMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_0a8d6ecb-5c42-45b4-996e-e33b914922c9" xlink:to="loc_us-gaap_CertificatesOfDepositMember_a10f706c-a457-4644-94be-fa097d63f16e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsMember_9488176b-1c12-40c5-aca3-e0056aaccb80" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MoneyMarketFundsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_0a8d6ecb-5c42-45b4-996e-e33b914922c9" xlink:to="loc_us-gaap_MoneyMarketFundsMember_9488176b-1c12-40c5-aca3-e0056aaccb80" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_SecuritiesAndOtherAssetsSegregatedUnderFederalAndOtherRegulationsAxis_eb24549e-706c-480a-80a6-2c1745cb6444" xlink:href="intl-20230630.xsd#intl_SecuritiesAndOtherAssetsSegregatedUnderFederalAndOtherRegulationsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_b0994aa8-a087-419a-a92e-5ccc19c12abf" xlink:to="loc_intl_SecuritiesAndOtherAssetsSegregatedUnderFederalAndOtherRegulationsAxis_eb24549e-706c-480a-80a6-2c1745cb6444" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_SecuritiesAndOtherAssetsSegregatedUnderFederalAndOtherRegulationsDomain_eb24549e-706c-480a-80a6-2c1745cb6444_default" xlink:href="intl-20230630.xsd#intl_SecuritiesAndOtherAssetsSegregatedUnderFederalAndOtherRegulationsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_intl_SecuritiesAndOtherAssetsSegregatedUnderFederalAndOtherRegulationsAxis_eb24549e-706c-480a-80a6-2c1745cb6444" xlink:to="loc_intl_SecuritiesAndOtherAssetsSegregatedUnderFederalAndOtherRegulationsDomain_eb24549e-706c-480a-80a6-2c1745cb6444_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_SecuritiesAndOtherAssetsSegregatedUnderFederalAndOtherRegulationsDomain_0d2c2b17-fb5e-444a-87bc-6422fae5064d" xlink:href="intl-20230630.xsd#intl_SecuritiesAndOtherAssetsSegregatedUnderFederalAndOtherRegulationsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_intl_SecuritiesAndOtherAssetsSegregatedUnderFederalAndOtherRegulationsAxis_eb24549e-706c-480a-80a6-2c1745cb6444" xlink:to="loc_intl_SecuritiesAndOtherAssetsSegregatedUnderFederalAndOtherRegulationsDomain_0d2c2b17-fb5e-444a-87bc-6422fae5064d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_CommoditiesWarehouseReceiptsMember_a2601aa8-b31c-4afe-a3c2-7f610520ff3e" xlink:href="intl-20230630.xsd#intl_CommoditiesWarehouseReceiptsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_intl_SecuritiesAndOtherAssetsSegregatedUnderFederalAndOtherRegulationsDomain_0d2c2b17-fb5e-444a-87bc-6422fae5064d" xlink:to="loc_intl_CommoditiesWarehouseReceiptsMember_a2601aa8-b31c-4afe-a3c2-7f610520ff3e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USGovernmentDebtSecuritiesMember_e9822a8a-d85d-449b-888c-7ead227f9422" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_USGovernmentDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_intl_SecuritiesAndOtherAssetsSegregatedUnderFederalAndOtherRegulationsDomain_0d2c2b17-fb5e-444a-87bc-6422fae5064d" xlink:to="loc_us-gaap_USGovernmentDebtSecuritiesMember_e9822a8a-d85d-449b-888c-7ead227f9422" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_DepositsAndReceivablesFromExchangeClearingOrganizationsAxis_be94b3dd-1985-4d13-acc7-7b36f9436f3d" xlink:href="intl-20230630.xsd#intl_DepositsAndReceivablesFromExchangeClearingOrganizationsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_b0994aa8-a087-419a-a92e-5ccc19c12abf" xlink:to="loc_intl_DepositsAndReceivablesFromExchangeClearingOrganizationsAxis_be94b3dd-1985-4d13-acc7-7b36f9436f3d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_DepositsAndReceivablesFromExchangeClearingOrganizationsDomain_be94b3dd-1985-4d13-acc7-7b36f9436f3d_default" xlink:href="intl-20230630.xsd#intl_DepositsAndReceivablesFromExchangeClearingOrganizationsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_intl_DepositsAndReceivablesFromExchangeClearingOrganizationsAxis_be94b3dd-1985-4d13-acc7-7b36f9436f3d" xlink:to="loc_intl_DepositsAndReceivablesFromExchangeClearingOrganizationsDomain_be94b3dd-1985-4d13-acc7-7b36f9436f3d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_DepositsAndReceivablesFromExchangeClearingOrganizationsDomain_69b6d476-e147-4d0c-97ce-c173e9ff4908" xlink:href="intl-20230630.xsd#intl_DepositsAndReceivablesFromExchangeClearingOrganizationsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_intl_DepositsAndReceivablesFromExchangeClearingOrganizationsAxis_be94b3dd-1985-4d13-acc7-7b36f9436f3d" xlink:to="loc_intl_DepositsAndReceivablesFromExchangeClearingOrganizationsDomain_69b6d476-e147-4d0c-97ce-c173e9ff4908" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USGovernmentDebtSecuritiesMember_2956d7ac-6b5d-4e86-8a97-4115067a37f3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_USGovernmentDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_intl_DepositsAndReceivablesFromExchangeClearingOrganizationsDomain_69b6d476-e147-4d0c-97ce-c173e9ff4908" xlink:to="loc_us-gaap_USGovernmentDebtSecuritiesMember_2956d7ac-6b5d-4e86-8a97-4115067a37f3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeMember_6186b52a-5076-45dd-8fb7-fa4e447c90da" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_intl_DepositsAndReceivablesFromExchangeClearingOrganizationsDomain_69b6d476-e147-4d0c-97ce-c173e9ff4908" xlink:to="loc_us-gaap_DerivativeMember_6186b52a-5076-45dd-8fb7-fa4e447c90da" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_DepositsAndReceivablesFromBrokerDealersClearingOrganizationsAndCounterpartiesAxis_650d4e04-00d1-48dc-9d37-351f495b781c" xlink:href="intl-20230630.xsd#intl_DepositsAndReceivablesFromBrokerDealersClearingOrganizationsAndCounterpartiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_b0994aa8-a087-419a-a92e-5ccc19c12abf" xlink:to="loc_intl_DepositsAndReceivablesFromBrokerDealersClearingOrganizationsAndCounterpartiesAxis_650d4e04-00d1-48dc-9d37-351f495b781c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_DepositsAndReceivablesFromBrokerDealersClearingOrganizationsAndCounterpartiesDomain_650d4e04-00d1-48dc-9d37-351f495b781c_default" xlink:href="intl-20230630.xsd#intl_DepositsAndReceivablesFromBrokerDealersClearingOrganizationsAndCounterpartiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_intl_DepositsAndReceivablesFromBrokerDealersClearingOrganizationsAndCounterpartiesAxis_650d4e04-00d1-48dc-9d37-351f495b781c" xlink:to="loc_intl_DepositsAndReceivablesFromBrokerDealersClearingOrganizationsAndCounterpartiesDomain_650d4e04-00d1-48dc-9d37-351f495b781c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_DepositsAndReceivablesFromBrokerDealersClearingOrganizationsAndCounterpartiesDomain_b6c06078-dd25-45e2-b8b4-3fd96d334b27" xlink:href="intl-20230630.xsd#intl_DepositsAndReceivablesFromBrokerDealersClearingOrganizationsAndCounterpartiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_intl_DepositsAndReceivablesFromBrokerDealersClearingOrganizationsAndCounterpartiesAxis_650d4e04-00d1-48dc-9d37-351f495b781c" xlink:to="loc_intl_DepositsAndReceivablesFromBrokerDealersClearingOrganizationsAndCounterpartiesDomain_b6c06078-dd25-45e2-b8b4-3fd96d334b27" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_TBAAndForwardSettlingSecuritiesMember_80103661-5360-4f9a-8e94-efcfd5789758" xlink:href="intl-20230630.xsd#intl_TBAAndForwardSettlingSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_intl_DepositsAndReceivablesFromBrokerDealersClearingOrganizationsAndCounterpartiesDomain_b6c06078-dd25-45e2-b8b4-3fd96d334b27" xlink:to="loc_intl_TBAAndForwardSettlingSecuritiesMember_80103661-5360-4f9a-8e94-efcfd5789758" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignGovernmentDebtSecuritiesMember_6066211e-f1bf-46d5-8aaf-68d90621c6e1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignGovernmentDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_intl_DepositsAndReceivablesFromBrokerDealersClearingOrganizationsAndCounterpartiesDomain_b6c06078-dd25-45e2-b8b4-3fd96d334b27" xlink:to="loc_us-gaap_ForeignGovernmentDebtSecuritiesMember_6066211e-f1bf-46d5-8aaf-68d90621c6e1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueAxis_d6d4b87e-f8f2-449b-a28d-f0624ac6e2ce" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_b0994aa8-a087-419a-a92e-5ccc19c12abf" xlink:to="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueAxis_d6d4b87e-f8f2-449b-a28d-f0624ac6e2ce" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedFairValueSecurityNameDomain_d6d4b87e-f8f2-449b-a28d-f0624ac6e2ce_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecurityOwnedAndSoldNotYetPurchasedFairValueSecurityNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueAxis_d6d4b87e-f8f2-449b-a28d-f0624ac6e2ce" xlink:to="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedFairValueSecurityNameDomain_d6d4b87e-f8f2-449b-a28d-f0624ac6e2ce_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedFairValueSecurityNameDomain_af7c8089-e1c0-4ea4-9705-039f52274c24" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecurityOwnedAndSoldNotYetPurchasedFairValueSecurityNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueAxis_d6d4b87e-f8f2-449b-a28d-f0624ac6e2ce" xlink:to="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedFairValueSecurityNameDomain_af7c8089-e1c0-4ea4-9705-039f52274c24" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesMember_70322253-05ef-4b70-920b-c224f8c9fcf6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquitySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedFairValueSecurityNameDomain_af7c8089-e1c0-4ea4-9705-039f52274c24" xlink:to="loc_us-gaap_EquitySecuritiesMember_70322253-05ef-4b70-920b-c224f8c9fcf6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesMember_e5a460d7-5d81-4a1d-84f3-57598bed68e6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedFairValueSecurityNameDomain_af7c8089-e1c0-4ea4-9705-039f52274c24" xlink:to="loc_us-gaap_DebtSecuritiesMember_e5a460d7-5d81-4a1d-84f3-57598bed68e6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USGovernmentDebtSecuritiesMember_540aba61-b56b-469e-b6a2-ca74bdd0f99b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_USGovernmentDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedFairValueSecurityNameDomain_af7c8089-e1c0-4ea4-9705-039f52274c24" xlink:to="loc_us-gaap_USGovernmentDebtSecuritiesMember_540aba61-b56b-469e-b6a2-ca74bdd0f99b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_bda2f02b-1228-409c-8933-ff6eb638b997" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_USGovernmentAgenciesDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedFairValueSecurityNameDomain_af7c8089-e1c0-4ea4-9705-039f52274c24" xlink:to="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_bda2f02b-1228-409c-8933-ff6eb638b997" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignGovernmentDebtSecuritiesMember_f3fb44c8-3441-46e1-8633-c6b976d7cf54" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignGovernmentDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedFairValueSecurityNameDomain_af7c8089-e1c0-4ea4-9705-039f52274c24" xlink:to="loc_us-gaap_ForeignGovernmentDebtSecuritiesMember_f3fb44c8-3441-46e1-8633-c6b976d7cf54" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MortgageBackedSecuritiesMember_479093f7-cacd-4b28-85e5-973aac36c747" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedFairValueSecurityNameDomain_af7c8089-e1c0-4ea4-9705-039f52274c24" xlink:to="loc_us-gaap_MortgageBackedSecuritiesMember_479093f7-cacd-4b28-85e5-973aac36c747" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_cfc20c97-61b0-458b-be46-5da11f6cce19" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedFairValueSecurityNameDomain_af7c8089-e1c0-4ea4-9705-039f52274c24" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_cfc20c97-61b0-458b-be46-5da11f6cce19" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeMember_c7c6ed38-f39c-43f6-b449-b7e78822de1f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedFairValueSecurityNameDomain_af7c8089-e1c0-4ea4-9705-039f52274c24" xlink:to="loc_us-gaap_DerivativeMember_c7c6ed38-f39c-43f6-b449-b7e78822de1f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_CommoditiesLeasesAndUnpricedPositionsMember_92c52284-15af-4340-9d62-57a169022468" xlink:href="intl-20230630.xsd#intl_CommoditiesLeasesAndUnpricedPositionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedFairValueSecurityNameDomain_af7c8089-e1c0-4ea4-9705-039f52274c24" xlink:to="loc_intl_CommoditiesLeasesAndUnpricedPositionsMember_92c52284-15af-4340-9d62-57a169022468" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_CommoditiesWarehouseReceiptsMember_8c4f4b76-fd25-41eb-b313-5cbc5ef66a15" xlink:href="intl-20230630.xsd#intl_CommoditiesWarehouseReceiptsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedFairValueSecurityNameDomain_af7c8089-e1c0-4ea4-9705-039f52274c24" xlink:to="loc_intl_CommoditiesWarehouseReceiptsMember_8c4f4b76-fd25-41eb-b313-5cbc5ef66a15" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_ExchangeFirmCommonStockMember_d40db33c-1f70-45a8-b450-5efd6cd4b75c" xlink:href="intl-20230630.xsd#intl_ExchangeFirmCommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedFairValueSecurityNameDomain_af7c8089-e1c0-4ea4-9705-039f52274c24" xlink:to="loc_intl_ExchangeFirmCommonStockMember_d40db33c-1f70-45a8-b450-5efd6cd4b75c" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_CashFlowHedgesMember_abfe6e26-ad45-4fe7-a1c3-b12abbb6370e" xlink:href="intl-20230630.xsd#intl_CashFlowHedgesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedFairValueSecurityNameDomain_af7c8089-e1c0-4ea4-9705-039f52274c24" xlink:to="loc_intl_CashFlowHedgesMember_abfe6e26-ad45-4fe7-a1c3-b12abbb6370e" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_MutualFundsAndOtherMember_bd36d206-4434-4724-be70-ba315da70a69" xlink:href="intl-20230630.xsd#intl_MutualFundsAndOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedFairValueSecurityNameDomain_af7c8089-e1c0-4ea4-9705-039f52274c24" xlink:to="loc_intl_MutualFundsAndOtherMember_bd36d206-4434-4724-be70-ba315da70a69" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_OtherMember_8b09e627-1c13-4695-b332-0eb252f09fa5" xlink:href="intl-20230630.xsd#intl_OtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedFairValueSecurityNameDomain_af7c8089-e1c0-4ea4-9705-039f52274c24" xlink:to="loc_intl_OtherMember_8b09e627-1c13-4695-b332-0eb252f09fa5" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_PhysicalCommoditiesInventoryAxis_ce80fc12-6336-471f-a528-a3c7452e8a08" xlink:href="intl-20230630.xsd#intl_PhysicalCommoditiesInventoryAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_b0994aa8-a087-419a-a92e-5ccc19c12abf" xlink:to="loc_intl_PhysicalCommoditiesInventoryAxis_ce80fc12-6336-471f-a528-a3c7452e8a08" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_PhysicalCommoditiesInventoryDomain_ce80fc12-6336-471f-a528-a3c7452e8a08_default" xlink:href="intl-20230630.xsd#intl_PhysicalCommoditiesInventoryDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_intl_PhysicalCommoditiesInventoryAxis_ce80fc12-6336-471f-a528-a3c7452e8a08" xlink:to="loc_intl_PhysicalCommoditiesInventoryDomain_ce80fc12-6336-471f-a528-a3c7452e8a08_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_PhysicalCommoditiesInventoryDomain_298e54c6-7103-4813-8bd0-1ff644037617" xlink:href="intl-20230630.xsd#intl_PhysicalCommoditiesInventoryDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_intl_PhysicalCommoditiesInventoryAxis_ce80fc12-6336-471f-a528-a3c7452e8a08" xlink:to="loc_intl_PhysicalCommoditiesInventoryDomain_298e54c6-7103-4813-8bd0-1ff644037617" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_PhysicalCommoditiesInventoryPreciousMetalsMember_0d074778-8b06-4c7e-8194-6c445c1c8cd1" xlink:href="intl-20230630.xsd#intl_PhysicalCommoditiesInventoryPreciousMetalsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_intl_PhysicalCommoditiesInventoryDomain_298e54c6-7103-4813-8bd0-1ff644037617" xlink:to="loc_intl_PhysicalCommoditiesInventoryPreciousMetalsMember_0d074778-8b06-4c7e-8194-6c445c1c8cd1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_PayablesToBrokerDealersClearingOrganizationsAndCounterpartiesAxis_7971afff-abbd-4f16-8291-dbd5c6c40a2c" xlink:href="intl-20230630.xsd#intl_PayablesToBrokerDealersClearingOrganizationsAndCounterpartiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_b0994aa8-a087-419a-a92e-5ccc19c12abf" xlink:to="loc_intl_PayablesToBrokerDealersClearingOrganizationsAndCounterpartiesAxis_7971afff-abbd-4f16-8291-dbd5c6c40a2c" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_PayablesToBrokerDealersClearingOrganizationsAndCounterpartiesDomain_7971afff-abbd-4f16-8291-dbd5c6c40a2c_default" xlink:href="intl-20230630.xsd#intl_PayablesToBrokerDealersClearingOrganizationsAndCounterpartiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_intl_PayablesToBrokerDealersClearingOrganizationsAndCounterpartiesAxis_7971afff-abbd-4f16-8291-dbd5c6c40a2c" xlink:to="loc_intl_PayablesToBrokerDealersClearingOrganizationsAndCounterpartiesDomain_7971afff-abbd-4f16-8291-dbd5c6c40a2c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_PayablesToBrokerDealersClearingOrganizationsAndCounterpartiesDomain_ae1f3b0b-5a18-497e-90ef-587f780cf087" xlink:href="intl-20230630.xsd#intl_PayablesToBrokerDealersClearingOrganizationsAndCounterpartiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_intl_PayablesToBrokerDealersClearingOrganizationsAndCounterpartiesAxis_7971afff-abbd-4f16-8291-dbd5c6c40a2c" xlink:to="loc_intl_PayablesToBrokerDealersClearingOrganizationsAndCounterpartiesDomain_ae1f3b0b-5a18-497e-90ef-587f780cf087" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_TBAAndForwardSettlingSecuritiesMember_4c4c330c-3f13-42af-9b15-74838605a0d5" xlink:href="intl-20230630.xsd#intl_TBAAndForwardSettlingSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_intl_PayablesToBrokerDealersClearingOrganizationsAndCounterpartiesDomain_ae1f3b0b-5a18-497e-90ef-587f780cf087" xlink:to="loc_intl_TBAAndForwardSettlingSecuritiesMember_4c4c330c-3f13-42af-9b15-74838605a0d5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeMember_a84a0f97-f930-4a79-993f-a09fcd89b9f0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_intl_PayablesToBrokerDealersClearingOrganizationsAndCounterpartiesDomain_ae1f3b0b-5a18-497e-90ef-587f780cf087" xlink:to="loc_us-gaap_DerivativeMember_a84a0f97-f930-4a79-993f-a09fcd89b9f0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_PayablesToBrokerDealersClearingOrganizationsAndCounterpartiesMember_f88ffd10-06ae-4851-9de2-6d8728ab7eff" xlink:href="intl-20230630.xsd#intl_PayablesToBrokerDealersClearingOrganizationsAndCounterpartiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_intl_PayablesToBrokerDealersClearingOrganizationsAndCounterpartiesDomain_ae1f3b0b-5a18-497e-90ef-587f780cf087" xlink:to="loc_intl_PayablesToBrokerDealersClearingOrganizationsAndCounterpartiesMember_f88ffd10-06ae-4851-9de2-6d8728ab7eff" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.intlfcstone.com/role/FinancialInstrumentswithOffBalanceSheetRiskandConcentrationsofCreditRiskNarrativeDetails" xlink:type="simple" xlink:href="intl-20230630.xsd#FinancialInstrumentswithOffBalanceSheetRiskandConcentrationsofCreditRiskNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.intlfcstone.com/role/FinancialInstrumentswithOffBalanceSheetRiskandConcentrationsofCreditRiskNarrativeDetails" xlink:type="extended" id="ie9bd11d01ac7401c91b14a23c4b38f8a_FinancialInstrumentswithOffBalanceSheetRiskandConcentrationsofCreditRiskNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueLineItems_53ce8f32-b811-4040-8b65-4751a194cee4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentsSoldNotYetPurchasedAtFairValue_5ed86a95-bb51-425b-a9ac-5a8328fed01d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentsSoldNotYetPurchasedAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueLineItems_53ce8f32-b811-4040-8b65-4751a194cee4" xlink:to="loc_us-gaap_FinancialInstrumentsSoldNotYetPurchasedAtFairValue_5ed86a95-bb51-425b-a9ac-5a8328fed01d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MaximumLengthOfTimeHedgedInCashFlowHedge1_5e0c8daf-f230-4972-b166-4eeab762dbcd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MaximumLengthOfTimeHedgedInCashFlowHedge1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueLineItems_53ce8f32-b811-4040-8b65-4751a194cee4" xlink:to="loc_us-gaap_MaximumLengthOfTimeHedgedInCashFlowHedge1_5e0c8daf-f230-4972-b166-4eeab762dbcd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueTable_f949b153-4ca1-4f2d-96f6-a6b1e6a2e170" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueLineItems_53ce8f32-b811-4040-8b65-4751a194cee4" xlink:to="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueTable_f949b153-4ca1-4f2d-96f6-a6b1e6a2e170" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_582c6356-3c24-4500-a4fc-12008dd240b8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueTable_f949b153-4ca1-4f2d-96f6-a6b1e6a2e170" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_582c6356-3c24-4500-a4fc-12008dd240b8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_582c6356-3c24-4500-a4fc-12008dd240b8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_582c6356-3c24-4500-a4fc-12008dd240b8" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_582c6356-3c24-4500-a4fc-12008dd240b8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_bd111190-8e4c-4d30-90b0-90953c5c17e9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_582c6356-3c24-4500-a4fc-12008dd240b8" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_bd111190-8e4c-4d30-90b0-90953c5c17e9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_34eaa871-c835-4d62-82f9-19bfc2674ea3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_bd111190-8e4c-4d30-90b0-90953c5c17e9" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_34eaa871-c835-4d62-82f9-19bfc2674ea3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueAxis_87fcc8e1-b4e0-426a-ab6b-fd1dd700bd97" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueTable_f949b153-4ca1-4f2d-96f6-a6b1e6a2e170" xlink:to="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueAxis_87fcc8e1-b4e0-426a-ab6b-fd1dd700bd97" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedFairValueSecurityNameDomain_87fcc8e1-b4e0-426a-ab6b-fd1dd700bd97_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecurityOwnedAndSoldNotYetPurchasedFairValueSecurityNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueAxis_87fcc8e1-b4e0-426a-ab6b-fd1dd700bd97" xlink:to="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedFairValueSecurityNameDomain_87fcc8e1-b4e0-426a-ab6b-fd1dd700bd97_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedFairValueSecurityNameDomain_13dd01b2-5c24-4046-9c97-0ab90bc43e43" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecurityOwnedAndSoldNotYetPurchasedFairValueSecurityNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueAxis_87fcc8e1-b4e0-426a-ab6b-fd1dd700bd97" xlink:to="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedFairValueSecurityNameDomain_13dd01b2-5c24-4046-9c97-0ab90bc43e43" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeMember_5c61ce8a-f53a-41ef-bd97-ab2641020dd8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedFairValueSecurityNameDomain_13dd01b2-5c24-4046-9c97-0ab90bc43e43" xlink:to="loc_us-gaap_DerivativeMember_5c61ce8a-f53a-41ef-bd97-ab2641020dd8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_d415de1f-b206-46f5-b9a4-838fd13d0002" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueTable_f949b153-4ca1-4f2d-96f6-a6b1e6a2e170" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_d415de1f-b206-46f5-b9a4-838fd13d0002" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_d415de1f-b206-46f5-b9a4-838fd13d0002_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_d415de1f-b206-46f5-b9a4-838fd13d0002" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_d415de1f-b206-46f5-b9a4-838fd13d0002_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_9fe43063-d03e-4c71-91c2-732fd91351bf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_d415de1f-b206-46f5-b9a4-838fd13d0002" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_9fe43063-d03e-4c71-91c2-732fd91351bf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateContractMember_a40d4270-adc5-435e-9f35-8d1f49c8f042" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestRateContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_9fe43063-d03e-4c71-91c2-732fd91351bf" xlink:to="loc_us-gaap_InterestRateContractMember_a40d4270-adc5-435e-9f35-8d1f49c8f042" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_ForeignCurrencyForwardsMember_569d1033-dc86-4f6e-a13a-d699413a78b1" xlink:href="intl-20230630.xsd#intl_ForeignCurrencyForwardsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_9fe43063-d03e-4c71-91c2-732fd91351bf" xlink:to="loc_intl_ForeignCurrencyForwardsMember_569d1033-dc86-4f6e-a13a-d699413a78b1" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.intlfcstone.com/role/FinancialInstrumentswithOffBalanceSheetRiskandConcentrationsofCreditRiskGrossDerivativeAssetsandLiabilitiesbyTypeandBalanceSheetLocationDetails" xlink:type="simple" xlink:href="intl-20230630.xsd#FinancialInstrumentswithOffBalanceSheetRiskandConcentrationsofCreditRiskGrossDerivativeAssetsandLiabilitiesbyTypeandBalanceSheetLocationDetails"/>
  <link:definitionLink xlink:role="http://www.intlfcstone.com/role/FinancialInstrumentswithOffBalanceSheetRiskandConcentrationsofCreditRiskGrossDerivativeAssetsandLiabilitiesbyTypeandBalanceSheetLocationDetails" xlink:type="extended" id="i39dadcbdadb64aecabaf029a098ba5ee_FinancialInstrumentswithOffBalanceSheetRiskandConcentrationsofCreditRiskGrossDerivativeAssetsandLiabilitiesbyTypeandBalanceSheetLocationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativesFairValueLineItems_32c06e78-f0aa-42cf-8acc-b4a3a8667795" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativesFairValueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_8428a7bc-6884-43d2-af7a-9fc4d8aba82b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeFairValueOfDerivativeAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_32c06e78-f0aa-42cf-8acc-b4a3a8667795" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_8428a7bc-6884-43d2-af7a-9fc4d8aba82b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_836bb2e5-d92d-4c4a-9b19-77cc1a7497a4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeFairValueOfDerivativeLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_32c06e78-f0aa-42cf-8acc-b4a3a8667795" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_836bb2e5-d92d-4c4a-9b19-77cc1a7497a4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetFairValueGrossLiabilityAndObligationToReturnCashOffset_f05e5b54-93bf-4b5e-a7d2-08993b252c6f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeAssetFairValueGrossLiabilityAndObligationToReturnCashOffset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_32c06e78-f0aa-42cf-8acc-b4a3a8667795" xlink:to="loc_us-gaap_DerivativeAssetFairValueGrossLiabilityAndObligationToReturnCashOffset_f05e5b54-93bf-4b5e-a7d2-08993b252c6f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset_df2b4a1e-4bbb-4284-b108-9123fe3e7b5b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_32c06e78-f0aa-42cf-8acc-b4a3a8667795" xlink:to="loc_us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset_df2b4a1e-4bbb-4284-b108-9123fe3e7b5b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeNet_2d4464b8-ce7c-4c80-83a0-a2f0a4b94a3b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeFairValueOfDerivativeNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_32c06e78-f0aa-42cf-8acc-b4a3a8667795" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeNet_2d4464b8-ce7c-4c80-83a0-a2f0a4b94a3b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNumberOfInstrumentsHeld_c9c716c8-1385-468c-a71f-cc850323123a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeNumberOfInstrumentsHeld"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_32c06e78-f0aa-42cf-8acc-b4a3a8667795" xlink:to="loc_us-gaap_DerivativeNumberOfInstrumentsHeld_c9c716c8-1385-468c-a71f-cc850323123a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_2ee70823-5f8f-4383-8d88-0f2f4b5879aa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_32c06e78-f0aa-42cf-8acc-b4a3a8667795" xlink:to="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_2ee70823-5f8f-4383-8d88-0f2f4b5879aa" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_6902ed36-6d6a-4f87-8228-d7b9dcc2f160" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_2ee70823-5f8f-4383-8d88-0f2f4b5879aa" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_6902ed36-6d6a-4f87-8228-d7b9dcc2f160" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_6902ed36-6d6a-4f87-8228-d7b9dcc2f160_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_6902ed36-6d6a-4f87-8228-d7b9dcc2f160" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_6902ed36-6d6a-4f87-8228-d7b9dcc2f160_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_a2aa2c07-fa5b-424b-95da-192f4225b52b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_6902ed36-6d6a-4f87-8228-d7b9dcc2f160" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_a2aa2c07-fa5b-424b-95da-192f4225b52b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_ExchangeTradedCommodityContractsMember_5764e2ce-d920-4502-a0b2-b4dfdcbd8d00" xlink:href="intl-20230630.xsd#intl_ExchangeTradedCommodityContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_a2aa2c07-fa5b-424b-95da-192f4225b52b" xlink:to="loc_intl_ExchangeTradedCommodityContractsMember_5764e2ce-d920-4502-a0b2-b4dfdcbd8d00" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_OverCounterOtcCommodityContractsMember_4b2216a7-b848-4fcb-83f0-3c915f67f044" xlink:href="intl-20230630.xsd#intl_OverCounterOtcCommodityContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_a2aa2c07-fa5b-424b-95da-192f4225b52b" xlink:to="loc_intl_OverCounterOtcCommodityContractsMember_4b2216a7-b848-4fcb-83f0-3c915f67f044" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeForwardMember_22405717-bea5-4b81-a154-96b9afaaa367" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignExchangeForwardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_a2aa2c07-fa5b-424b-95da-192f4225b52b" xlink:to="loc_us-gaap_ForeignExchangeForwardMember_22405717-bea5-4b81-a154-96b9afaaa367" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_OverCounterOtcForeignExchangeContractsMember_92d7ae16-4844-4c10-95dc-c0fee605c2f1" xlink:href="intl-20230630.xsd#intl_OverCounterOtcForeignExchangeContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_a2aa2c07-fa5b-424b-95da-192f4225b52b" xlink:to="loc_intl_OverCounterOtcForeignExchangeContractsMember_92d7ae16-4844-4c10-95dc-c0fee605c2f1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_ExchangeTradedInterestRateContractsMember_d4ae119b-e7f3-4f4b-baa6-93aac030f4a3" xlink:href="intl-20230630.xsd#intl_ExchangeTradedInterestRateContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_a2aa2c07-fa5b-424b-95da-192f4225b52b" xlink:to="loc_intl_ExchangeTradedInterestRateContractsMember_d4ae119b-e7f3-4f4b-baa6-93aac030f4a3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateContractMember_e6d5442e-2c59-48da-9af0-900a96feeebe" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestRateContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_a2aa2c07-fa5b-424b-95da-192f4225b52b" xlink:to="loc_us-gaap_InterestRateContractMember_e6d5442e-2c59-48da-9af0-900a96feeebe" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityContractMember_9664f031-9e78-4b0b-a304-798a7124add1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_a2aa2c07-fa5b-424b-95da-192f4225b52b" xlink:to="loc_us-gaap_EquityContractMember_9664f031-9e78-4b0b-a304-798a7124add1" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_OTCEquityAndIndicesContractMember_60348713-3245-4a08-9bcb-8514b3721e4c" xlink:href="intl-20230630.xsd#intl_OTCEquityAndIndicesContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_a2aa2c07-fa5b-424b-95da-192f4225b52b" xlink:to="loc_intl_OTCEquityAndIndicesContractMember_60348713-3245-4a08-9bcb-8514b3721e4c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_TBAAndForwardSettlingSecuritiesMember_7386153b-7acc-417a-aef7-ebe4980597a3" xlink:href="intl-20230630.xsd#intl_TBAAndForwardSettlingSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_a2aa2c07-fa5b-424b-95da-192f4225b52b" xlink:to="loc_intl_TBAAndForwardSettlingSecuritiesMember_7386153b-7acc-417a-aef7-ebe4980597a3" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_ForeignCurrencyForwardsMember_f0f9391a-a219-4c0a-a70b-4ca44b07319e" xlink:href="intl-20230630.xsd#intl_ForeignCurrencyForwardsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_a2aa2c07-fa5b-424b-95da-192f4225b52b" xlink:to="loc_intl_ForeignCurrencyForwardsMember_f0f9391a-a219-4c0a-a70b-4ca44b07319e" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_5e66f794-af2c-4047-949d-7ec1b159f0db" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_2ee70823-5f8f-4383-8d88-0f2f4b5879aa" xlink:to="loc_us-gaap_HedgingDesignationAxis_5e66f794-af2c-4047-949d-7ec1b159f0db" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_5e66f794-af2c-4047-949d-7ec1b159f0db_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_5e66f794-af2c-4047-949d-7ec1b159f0db" xlink:to="loc_us-gaap_HedgingDesignationDomain_5e66f794-af2c-4047-949d-7ec1b159f0db_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_c58ce596-e657-44d0-9413-000a51b292b3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_5e66f794-af2c-4047-949d-7ec1b159f0db" xlink:to="loc_us-gaap_HedgingDesignationDomain_c58ce596-e657-44d0-9413-000a51b292b3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NondesignatedMember_455ec8f2-ce5d-4b9d-b141-9b6f8705f16a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NondesignatedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_c58ce596-e657-44d0-9413-000a51b292b3" xlink:to="loc_us-gaap_NondesignatedMember_455ec8f2-ce5d-4b9d-b141-9b6f8705f16a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_1d2e6580-56d0-4206-8639-84f26482a463" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_c58ce596-e657-44d0-9413-000a51b292b3" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_1d2e6580-56d0-4206-8639-84f26482a463" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_971fd061-0016-4269-977d-758894f15f44" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BalanceSheetLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_2ee70823-5f8f-4383-8d88-0f2f4b5879aa" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_971fd061-0016-4269-977d-758894f15f44" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_971fd061-0016-4269-977d-758894f15f44_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_971fd061-0016-4269-977d-758894f15f44" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_971fd061-0016-4269-977d-758894f15f44_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_60f37817-c897-46c0-be0a-43d637ce11d5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_971fd061-0016-4269-977d-758894f15f44" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_60f37817-c897-46c0-be0a-43d637ce11d5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_DepositsAndReceivablesFromExchangeClearingOrganizationsMember_a48b2b89-c428-4348-b83a-baf51cd36bc0" xlink:href="intl-20230630.xsd#intl_DepositsAndReceivablesFromExchangeClearingOrganizationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_60f37817-c897-46c0-be0a-43d637ce11d5" xlink:to="loc_intl_DepositsAndReceivablesFromExchangeClearingOrganizationsMember_a48b2b89-c428-4348-b83a-baf51cd36bc0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_ReceivableFromClientsNetMember_c5fd545f-d1c6-43d8-882d-ccc975789c48" xlink:href="intl-20230630.xsd#intl_ReceivableFromClientsNetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_60f37817-c897-46c0-be0a-43d637ce11d5" xlink:to="loc_intl_ReceivableFromClientsNetMember_c5fd545f-d1c6-43d8-882d-ccc975789c48" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_FinancialInstrumentsOwnedMember_e797146d-5581-4da2-a348-add1fa8f4371" xlink:href="intl-20230630.xsd#intl_FinancialInstrumentsOwnedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_60f37817-c897-46c0-be0a-43d637ce11d5" xlink:to="loc_intl_FinancialInstrumentsOwnedMember_e797146d-5581-4da2-a348-add1fa8f4371" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_PayablesToClientsMember_288ec70e-53f1-4dd1-aae0-8d8da2f541e9" xlink:href="intl-20230630.xsd#intl_PayablesToClientsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_60f37817-c897-46c0-be0a-43d637ce11d5" xlink:to="loc_intl_PayablesToClientsMember_288ec70e-53f1-4dd1-aae0-8d8da2f541e9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_PayablesToBrokerDealersClearingOrganizationsAndCounterpartiesMember_3526d00a-3404-4dbc-8db6-8859c0184fd9" xlink:href="intl-20230630.xsd#intl_PayablesToBrokerDealersClearingOrganizationsAndCounterpartiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_60f37817-c897-46c0-be0a-43d637ce11d5" xlink:to="loc_intl_PayablesToBrokerDealersClearingOrganizationsAndCounterpartiesMember_3526d00a-3404-4dbc-8db6-8859c0184fd9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_FinancialInstrumentSoldNotYetPurchasedMember_4e972e62-8de3-4e69-b195-44234335ca5e" xlink:href="intl-20230630.xsd#intl_FinancialInstrumentSoldNotYetPurchasedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_60f37817-c897-46c0-be0a-43d637ce11d5" xlink:to="loc_intl_FinancialInstrumentSoldNotYetPurchasedMember_4e972e62-8de3-4e69-b195-44234335ca5e" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.intlfcstone.com/role/FinancialInstrumentswithOffBalanceSheetRiskandConcentrationsofCreditRiskFairValuesofDerivativeInstrumentsDesignatedforHedgingHeldDetails" xlink:type="simple" xlink:href="intl-20230630.xsd#FinancialInstrumentswithOffBalanceSheetRiskandConcentrationsofCreditRiskFairValuesofDerivativeInstrumentsDesignatedforHedgingHeldDetails"/>
  <link:definitionLink xlink:role="http://www.intlfcstone.com/role/FinancialInstrumentswithOffBalanceSheetRiskandConcentrationsofCreditRiskFairValuesofDerivativeInstrumentsDesignatedforHedgingHeldDetails" xlink:type="extended" id="i47289c84431c43efbfe9c0baa3594067_FinancialInstrumentswithOffBalanceSheetRiskandConcentrationsofCreditRiskFairValuesofDerivativeInstrumentsDesignatedforHedgingHeldDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativesFairValueLineItems_adc14f2f-f35d-41c7-94f4-4cea284ef535" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativesFairValueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_b514a3ec-b905-4647-a2c3-b02f87914b05" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeFairValueOfDerivativeAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_adc14f2f-f35d-41c7-94f4-4cea284ef535" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_b514a3ec-b905-4647-a2c3-b02f87914b05" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_OtherComprehensiveIncomeLossDerivativeAssetsCashFlowHedgeGainLossReclassificationBeforeTax_c01aa011-d533-4411-9a04-e0bfb9bc9d8c" xlink:href="intl-20230630.xsd#intl_OtherComprehensiveIncomeLossDerivativeAssetsCashFlowHedgeGainLossReclassificationBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_adc14f2f-f35d-41c7-94f4-4cea284ef535" xlink:to="loc_intl_OtherComprehensiveIncomeLossDerivativeAssetsCashFlowHedgeGainLossReclassificationBeforeTax_c01aa011-d533-4411-9a04-e0bfb9bc9d8c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_ec5194b4-068f-4e35-8254-6a1b453925f7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeFairValueOfDerivativeLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_adc14f2f-f35d-41c7-94f4-4cea284ef535" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_ec5194b4-068f-4e35-8254-6a1b453925f7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_OtherComprehensiveIncomeLossDerivativeLiabilitiesCashFlowHedgeGainLossReclassificationBeforeTax_1dad9f7d-36f1-4437-a3da-94a2609f24f6" xlink:href="intl-20230630.xsd#intl_OtherComprehensiveIncomeLossDerivativeLiabilitiesCashFlowHedgeGainLossReclassificationBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_adc14f2f-f35d-41c7-94f4-4cea284ef535" xlink:to="loc_intl_OtherComprehensiveIncomeLossDerivativeLiabilitiesCashFlowHedgeGainLossReclassificationBeforeTax_1dad9f7d-36f1-4437-a3da-94a2609f24f6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_7e1b4043-7be0-40de-bd72-848fc3d87209" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_adc14f2f-f35d-41c7-94f4-4cea284ef535" xlink:to="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_7e1b4043-7be0-40de-bd72-848fc3d87209" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_8f9aea1d-de40-458a-9924-b25140d8d21f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_7e1b4043-7be0-40de-bd72-848fc3d87209" xlink:to="loc_us-gaap_HedgingDesignationAxis_8f9aea1d-de40-458a-9924-b25140d8d21f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_8f9aea1d-de40-458a-9924-b25140d8d21f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_8f9aea1d-de40-458a-9924-b25140d8d21f" xlink:to="loc_us-gaap_HedgingDesignationDomain_8f9aea1d-de40-458a-9924-b25140d8d21f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_d7a3d241-af16-4a15-ba17-331d4ec6fb59" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_8f9aea1d-de40-458a-9924-b25140d8d21f" xlink:to="loc_us-gaap_HedgingDesignationDomain_d7a3d241-af16-4a15-ba17-331d4ec6fb59" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_f4601db3-1982-4000-be4a-dce95e30c6ba" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_d7a3d241-af16-4a15-ba17-331d4ec6fb59" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_f4601db3-1982-4000-be4a-dce95e30c6ba" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_4ecd2c40-72c5-427c-b759-d25958929923" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_7e1b4043-7be0-40de-bd72-848fc3d87209" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_4ecd2c40-72c5-427c-b759-d25958929923" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_4ecd2c40-72c5-427c-b759-d25958929923_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_4ecd2c40-72c5-427c-b759-d25958929923" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_4ecd2c40-72c5-427c-b759-d25958929923_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_eaab2455-aed2-43d7-ada5-05d841447e50" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_4ecd2c40-72c5-427c-b759-d25958929923" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_eaab2455-aed2-43d7-ada5-05d841447e50" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_ForeignCurrencyForwardsMember_288e88e1-79d3-4c6f-be05-b2da3d787216" xlink:href="intl-20230630.xsd#intl_ForeignCurrencyForwardsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_eaab2455-aed2-43d7-ada5-05d841447e50" xlink:to="loc_intl_ForeignCurrencyForwardsMember_288e88e1-79d3-4c6f-be05-b2da3d787216" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateContractMember_cf082ccc-a8ac-4537-853d-61b20502004e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestRateContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_eaab2455-aed2-43d7-ada5-05d841447e50" xlink:to="loc_us-gaap_InterestRateContractMember_cf082ccc-a8ac-4537-853d-61b20502004e" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.intlfcstone.com/role/FinancialInstrumentswithOffBalanceSheetRiskandConcentrationsofCreditRiskNotionalValuesForDerivativesInstrumentDetails" xlink:type="simple" xlink:href="intl-20230630.xsd#FinancialInstrumentswithOffBalanceSheetRiskandConcentrationsofCreditRiskNotionalValuesForDerivativesInstrumentDetails"/>
  <link:definitionLink xlink:role="http://www.intlfcstone.com/role/FinancialInstrumentswithOffBalanceSheetRiskandConcentrationsofCreditRiskNotionalValuesForDerivativesInstrumentDetails" xlink:type="extended" id="i25c8af3bef984b8d9fff02f1f0e9d94f_FinancialInstrumentswithOffBalanceSheetRiskandConcentrationsofCreditRiskNotionalValuesForDerivativesInstrumentDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueLineItems_f00ed077-7c0e-43b3-91b6-0b8a2b1bac00" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_02bd94bb-28c3-4c34-bdca-3faffbc263ca" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueLineItems_f00ed077-7c0e-43b3-91b6-0b8a2b1bac00" xlink:to="loc_us-gaap_DerivativeNotionalAmount_02bd94bb-28c3-4c34-bdca-3faffbc263ca" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueTable_2fc5a5c8-4d60-4c86-bf9e-6b60e11b9cc6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueLineItems_f00ed077-7c0e-43b3-91b6-0b8a2b1bac00" xlink:to="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueTable_2fc5a5c8-4d60-4c86-bf9e-6b60e11b9cc6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_da40ece3-902a-4b92-9eb6-237e8e3a5969" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueTable_2fc5a5c8-4d60-4c86-bf9e-6b60e11b9cc6" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_da40ece3-902a-4b92-9eb6-237e8e3a5969" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_da40ece3-902a-4b92-9eb6-237e8e3a5969_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_da40ece3-902a-4b92-9eb6-237e8e3a5969" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_da40ece3-902a-4b92-9eb6-237e8e3a5969_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_141ecde8-960a-4314-9b6e-ba68a0b481b6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_da40ece3-902a-4b92-9eb6-237e8e3a5969" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_141ecde8-960a-4314-9b6e-ba68a0b481b6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateContractMember_ee333038-1f2d-4276-8bae-c0756f540fb4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestRateContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_141ecde8-960a-4314-9b6e-ba68a0b481b6" xlink:to="loc_us-gaap_InterestRateContractMember_ee333038-1f2d-4276-8bae-c0756f540fb4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_ForeignCurrencyForwardsMember_097bc30f-2147-45d0-b78d-f2fcca97cb98" xlink:href="intl-20230630.xsd#intl_ForeignCurrencyForwardsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_141ecde8-960a-4314-9b6e-ba68a0b481b6" xlink:to="loc_intl_ForeignCurrencyForwardsMember_097bc30f-2147-45d0-b78d-f2fcca97cb98" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_fed75e83-474e-4e18-83d0-3f672a839170" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueTable_2fc5a5c8-4d60-4c86-bf9e-6b60e11b9cc6" xlink:to="loc_us-gaap_HedgingDesignationAxis_fed75e83-474e-4e18-83d0-3f672a839170" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_fed75e83-474e-4e18-83d0-3f672a839170_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_fed75e83-474e-4e18-83d0-3f672a839170" xlink:to="loc_us-gaap_HedgingDesignationDomain_fed75e83-474e-4e18-83d0-3f672a839170_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_2f5179c6-2efe-4ca5-80fd-d3d88064a556" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_fed75e83-474e-4e18-83d0-3f672a839170" xlink:to="loc_us-gaap_HedgingDesignationDomain_2f5179c6-2efe-4ca5-80fd-d3d88064a556" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_fc79b13d-f59f-4788-9f13-cc5e3d073a96" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_2f5179c6-2efe-4ca5-80fd-d3d88064a556" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_fc79b13d-f59f-4788-9f13-cc5e3d073a96" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CurrencyAxis_e688fa8f-8b5d-4991-85bd-a0b7088fdb2b" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CurrencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueTable_2fc5a5c8-4d60-4c86-bf9e-6b60e11b9cc6" xlink:to="loc_srt_CurrencyAxis_e688fa8f-8b5d-4991-85bd-a0b7088fdb2b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_AllCurrenciesDomain_e688fa8f-8b5d-4991-85bd-a0b7088fdb2b_default" xlink:href="https://xbrl.sec.gov/currency/2023/currency-2023.xsd#currency_AllCurrenciesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CurrencyAxis_e688fa8f-8b5d-4991-85bd-a0b7088fdb2b" xlink:to="loc_currency_AllCurrenciesDomain_e688fa8f-8b5d-4991-85bd-a0b7088fdb2b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_AllCurrenciesDomain_4f8f0080-5284-42f1-a5c6-111ec7952c96" xlink:href="https://xbrl.sec.gov/currency/2023/currency-2023.xsd#currency_AllCurrenciesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CurrencyAxis_e688fa8f-8b5d-4991-85bd-a0b7088fdb2b" xlink:to="loc_currency_AllCurrenciesDomain_4f8f0080-5284-42f1-a5c6-111ec7952c96" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_PLN_4e389d6d-2042-48bd-9468-4ebff7a4abbf" xlink:href="https://xbrl.sec.gov/currency/2023/currency-2023.xsd#currency_PLN"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_currency_AllCurrenciesDomain_4f8f0080-5284-42f1-a5c6-111ec7952c96" xlink:to="loc_currency_PLN_4e389d6d-2042-48bd-9468-4ebff7a4abbf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_GBP_f8afdcb9-676d-4f3c-8d3d-8b8e975e73c3" xlink:href="https://xbrl.sec.gov/currency/2023/currency-2023.xsd#currency_GBP"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_currency_AllCurrenciesDomain_4f8f0080-5284-42f1-a5c6-111ec7952c96" xlink:to="loc_currency_GBP_f8afdcb9-676d-4f3c-8d3d-8b8e975e73c3" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.intlfcstone.com/role/FinancialInstrumentswithOffBalanceSheetRiskandConcentrationsofCreditRiskIncomeStatementEffectsofDerivativeInstrumentsDetails" xlink:type="simple" xlink:href="intl-20230630.xsd#FinancialInstrumentswithOffBalanceSheetRiskandConcentrationsofCreditRiskIncomeStatementEffectsofDerivativeInstrumentsDetails"/>
  <link:definitionLink xlink:role="http://www.intlfcstone.com/role/FinancialInstrumentswithOffBalanceSheetRiskandConcentrationsofCreditRiskIncomeStatementEffectsofDerivativeInstrumentsDetails" xlink:type="extended" id="i120ca101d2184dc6a5fefb4f66908c26_FinancialInstrumentswithOffBalanceSheetRiskandConcentrationsofCreditRiskIncomeStatementEffectsofDerivativeInstrumentsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_8da297ab-86f6-4507-948f-b73b0b8d7a3a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeGainLossOnDerivativeNet_7d4d0860-9348-44e6-9a0f-89149f5f0f3f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeGainLossOnDerivativeNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_8da297ab-86f6-4507-948f-b73b0b8d7a3a" xlink:to="loc_us-gaap_DerivativeGainLossOnDerivativeNet_7d4d0860-9348-44e6-9a0f-89149f5f0f3f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax_62592697-a8ac-4032-b19e-60985d3281b4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_8da297ab-86f6-4507-948f-b73b0b8d7a3a" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax_62592697-a8ac-4032-b19e-60985d3281b4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTaxForecastedTransactionNotProbable_becb20b1-33fa-47f3-b89b-017f2e6697c1" xlink:href="intl-20230630.xsd#intl_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTaxForecastedTransactionNotProbable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_8da297ab-86f6-4507-948f-b73b0b8d7a3a" xlink:to="loc_intl_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTaxForecastedTransactionNotProbable_becb20b1-33fa-47f3-b89b-017f2e6697c1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_394f9a7a-66a6-434a-932e-e3554684a804" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_8da297ab-86f6-4507-948f-b73b0b8d7a3a" xlink:to="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_394f9a7a-66a6-434a-932e-e3554684a804" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_a6405277-97ef-4afb-9a75-d1b73795c0cd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_394f9a7a-66a6-434a-932e-e3554684a804" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_a6405277-97ef-4afb-9a75-d1b73795c0cd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_a6405277-97ef-4afb-9a75-d1b73795c0cd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_a6405277-97ef-4afb-9a75-d1b73795c0cd" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_a6405277-97ef-4afb-9a75-d1b73795c0cd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_fa23ff93-ba92-439a-9c13-456bf7c3b968" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_a6405277-97ef-4afb-9a75-d1b73795c0cd" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_fa23ff93-ba92-439a-9c13-456bf7c3b968" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateContractMember_5638375e-286a-4cd1-b5df-9693bd719506" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestRateContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_fa23ff93-ba92-439a-9c13-456bf7c3b968" xlink:to="loc_us-gaap_InterestRateContractMember_5638375e-286a-4cd1-b5df-9693bd719506" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_ForeignCurrencyForwardsMember_6efa3701-04ae-4034-8290-7086cf01a83b" xlink:href="intl-20230630.xsd#intl_ForeignCurrencyForwardsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_fa23ff93-ba92-439a-9c13-456bf7c3b968" xlink:to="loc_intl_ForeignCurrencyForwardsMember_6efa3701-04ae-4034-8290-7086cf01a83b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_0e420501-2c6b-4e76-b2b0-65456d690e46" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_394f9a7a-66a6-434a-932e-e3554684a804" xlink:to="loc_us-gaap_HedgingDesignationAxis_0e420501-2c6b-4e76-b2b0-65456d690e46" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_0e420501-2c6b-4e76-b2b0-65456d690e46_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_0e420501-2c6b-4e76-b2b0-65456d690e46" xlink:to="loc_us-gaap_HedgingDesignationDomain_0e420501-2c6b-4e76-b2b0-65456d690e46_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_3b59c968-7fff-4106-8f20-1316767ddff6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_0e420501-2c6b-4e76-b2b0-65456d690e46" xlink:to="loc_us-gaap_HedgingDesignationDomain_3b59c968-7fff-4106-8f20-1316767ddff6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_5c09abef-49c1-41cd-818a-ec1d4e47643e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_3b59c968-7fff-4106-8f20-1316767ddff6" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_5c09abef-49c1-41cd-818a-ec1d4e47643e" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.intlfcstone.com/role/FinancialInstrumentswithOffBalanceSheetRiskandConcentrationsofCreditRiskAccumulatedOtherComprehensiveIncomeEffectsofDerivativeInstrumentsDetails" xlink:type="simple" xlink:href="intl-20230630.xsd#FinancialInstrumentswithOffBalanceSheetRiskandConcentrationsofCreditRiskAccumulatedOtherComprehensiveIncomeEffectsofDerivativeInstrumentsDetails"/>
  <link:definitionLink xlink:role="http://www.intlfcstone.com/role/FinancialInstrumentswithOffBalanceSheetRiskandConcentrationsofCreditRiskAccumulatedOtherComprehensiveIncomeEffectsofDerivativeInstrumentsDetails" xlink:type="extended" id="ib048655d787741f7bee2c200ec20dbc9_FinancialInstrumentswithOffBalanceSheetRiskandConcentrationsofCreditRiskAccumulatedOtherComprehensiveIncomeEffectsofDerivativeInstrumentsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_918edc52-507a-4d6e-882d-f31b1e69b20a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax_46629b89-cf10-461c-8307-90b2393a4b10" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_918edc52-507a-4d6e-882d-f31b1e69b20a" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax_46629b89-cf10-461c-8307-90b2393a4b10" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax_a46dc5f9-190d-4d0f-9cb2-fa14843c370a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_918edc52-507a-4d6e-882d-f31b1e69b20a" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax_a46dc5f9-190d-4d0f-9cb2-fa14843c370a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_9d0f3936-b526-43d2-988e-4bbd3505d32d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_918edc52-507a-4d6e-882d-f31b1e69b20a" xlink:to="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_9d0f3936-b526-43d2-988e-4bbd3505d32d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_9e24cc9d-a539-46d1-9d0c-526751dd33be" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_9d0f3936-b526-43d2-988e-4bbd3505d32d" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_9e24cc9d-a539-46d1-9d0c-526751dd33be" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_9e24cc9d-a539-46d1-9d0c-526751dd33be_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_9e24cc9d-a539-46d1-9d0c-526751dd33be" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_9e24cc9d-a539-46d1-9d0c-526751dd33be_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_123c6116-d052-4cef-821d-aa3982cc650f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_9e24cc9d-a539-46d1-9d0c-526751dd33be" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_123c6116-d052-4cef-821d-aa3982cc650f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateContractMember_07cd1d0a-d0ea-4c2b-b3a2-284deb6cfbd4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestRateContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_123c6116-d052-4cef-821d-aa3982cc650f" xlink:to="loc_us-gaap_InterestRateContractMember_07cd1d0a-d0ea-4c2b-b3a2-284deb6cfbd4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_ForeignCurrencyForwardsMember_9e84708f-3fa0-4cfa-b66d-955c05744a94" xlink:href="intl-20230630.xsd#intl_ForeignCurrencyForwardsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_123c6116-d052-4cef-821d-aa3982cc650f" xlink:to="loc_intl_ForeignCurrencyForwardsMember_9e84708f-3fa0-4cfa-b66d-955c05744a94" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.intlfcstone.com/role/FinancialInstrumentswithOffBalanceSheetRiskandConcentrationsofCreditRiskRealizedGainsLossesonDerivativeContractsDetails" xlink:type="simple" xlink:href="intl-20230630.xsd#FinancialInstrumentswithOffBalanceSheetRiskandConcentrationsofCreditRiskRealizedGainsLossesonDerivativeContractsDetails"/>
  <link:definitionLink xlink:role="http://www.intlfcstone.com/role/FinancialInstrumentswithOffBalanceSheetRiskandConcentrationsofCreditRiskRealizedGainsLossesonDerivativeContractsDetails" xlink:type="extended" id="id195e12d5c5149319c73a4c54ef81b43_FinancialInstrumentswithOffBalanceSheetRiskandConcentrationsofCreditRiskRealizedGainsLossesonDerivativeContractsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_36ebcf00-5e94-40f6-8be6-4010baaf0e82" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentsGainLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeGainLossOnDerivativeNet_82464dd3-a4d6-4455-b8d2-0cb717fae150" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeGainLossOnDerivativeNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_36ebcf00-5e94-40f6-8be6-4010baaf0e82" xlink:to="loc_us-gaap_DerivativeGainLossOnDerivativeNet_82464dd3-a4d6-4455-b8d2-0cb717fae150" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_ed31c77c-4eb1-41f6-8534-75e5de1fc829" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_36ebcf00-5e94-40f6-8be6-4010baaf0e82" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_ed31c77c-4eb1-41f6-8534-75e5de1fc829" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_2f69df34-79d6-4ebb-ad6e-e2d8b6ac1913" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_ed31c77c-4eb1-41f6-8534-75e5de1fc829" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_2f69df34-79d6-4ebb-ad6e-e2d8b6ac1913" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_2f69df34-79d6-4ebb-ad6e-e2d8b6ac1913_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_2f69df34-79d6-4ebb-ad6e-e2d8b6ac1913" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_2f69df34-79d6-4ebb-ad6e-e2d8b6ac1913_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_1fd87697-f32f-41ff-9875-0905ae18926c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_2f69df34-79d6-4ebb-ad6e-e2d8b6ac1913" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_1fd87697-f32f-41ff-9875-0905ae18926c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommodityContractMember_0860ae81-fd7b-4f73-9a73-0ec1bcc131d6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommodityContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_1fd87697-f32f-41ff-9875-0905ae18926c" xlink:to="loc_us-gaap_CommodityContractMember_0860ae81-fd7b-4f73-9a73-0ec1bcc131d6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeForwardMember_e2cf4fec-b6d7-4f88-a127-84c8adf084bf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignExchangeForwardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_1fd87697-f32f-41ff-9875-0905ae18926c" xlink:to="loc_us-gaap_ForeignExchangeForwardMember_e2cf4fec-b6d7-4f88-a127-84c8adf084bf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateContractMember_923e47cd-b981-44ab-8ffb-8ecf27e59243" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestRateContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_1fd87697-f32f-41ff-9875-0905ae18926c" xlink:to="loc_us-gaap_InterestRateContractMember_923e47cd-b981-44ab-8ffb-8ecf27e59243" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_TBAAndForwardSettlingSecuritiesMember_685268a0-75a9-46a9-8afc-ff7f1df08a9f" xlink:href="intl-20230630.xsd#intl_TBAAndForwardSettlingSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_1fd87697-f32f-41ff-9875-0905ae18926c" xlink:to="loc_intl_TBAAndForwardSettlingSecuritiesMember_685268a0-75a9-46a9-8afc-ff7f1df08a9f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeMember_aeb7f9b5-22fd-4ebc-b93a-1d670f010b72" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_1fd87697-f32f-41ff-9875-0905ae18926c" xlink:to="loc_us-gaap_DerivativeMember_aeb7f9b5-22fd-4ebc-b93a-1d670f010b72" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.intlfcstone.com/role/PhysicalCommoditiesInventoryPhysicalCommoditiesInventoryDetails" xlink:type="simple" xlink:href="intl-20230630.xsd#PhysicalCommoditiesInventoryPhysicalCommoditiesInventoryDetails"/>
  <link:definitionLink xlink:role="http://www.intlfcstone.com/role/PhysicalCommoditiesInventoryPhysicalCommoditiesInventoryDetails" xlink:type="extended" id="ib03e10e23cb54a67a7fd21019708b683_PhysicalCommoditiesInventoryPhysicalCommoditiesInventoryDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryLineItems_31b2be19-3334-404a-b9ad-ccfcdac072fa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InventoryLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AgriculturalRelatedInventory_ad4f2250-2f13-4e95-b653-98af21d22dcf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AgriculturalRelatedInventory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InventoryLineItems_31b2be19-3334-404a-b9ad-ccfcdac072fa" xlink:to="loc_us-gaap_AgriculturalRelatedInventory_ad4f2250-2f13-4e95-b653-98af21d22dcf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_PhysicalCommoditiesInventoryAtFairValue_b350a35d-7de0-419d-be3b-d3cc0d6c2d09" xlink:href="intl-20230630.xsd#intl_PhysicalCommoditiesInventoryAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InventoryLineItems_31b2be19-3334-404a-b9ad-ccfcdac072fa" xlink:to="loc_intl_PhysicalCommoditiesInventoryAtFairValue_b350a35d-7de0-419d-be3b-d3cc0d6c2d09" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryFinishedGoodsNetOfReserves_4858cfb5-f3bf-49b0-9afb-345678cbb014" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InventoryFinishedGoodsNetOfReserves"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InventoryLineItems_31b2be19-3334-404a-b9ad-ccfcdac072fa" xlink:to="loc_us-gaap_InventoryFinishedGoodsNetOfReserves_4858cfb5-f3bf-49b0-9afb-345678cbb014" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryNet_f1eaefe7-e020-4723-8847-cf40ef9fac95" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InventoryNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InventoryLineItems_31b2be19-3334-404a-b9ad-ccfcdac072fa" xlink:to="loc_us-gaap_InventoryNet_f1eaefe7-e020-4723-8847-cf40ef9fac95" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryCurrentTable_ee52d4d7-9b36-4b45-8438-819e57b66dcf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InventoryCurrentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_InventoryLineItems_31b2be19-3334-404a-b9ad-ccfcdac072fa" xlink:to="loc_us-gaap_InventoryCurrentTable_ee52d4d7-9b36-4b45-8438-819e57b66dcf" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_PhysicalCommoditiesInventoryAxis_55b0390f-0110-46f2-92db-02a302038064" xlink:href="intl-20230630.xsd#intl_PhysicalCommoditiesInventoryAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_InventoryCurrentTable_ee52d4d7-9b36-4b45-8438-819e57b66dcf" xlink:to="loc_intl_PhysicalCommoditiesInventoryAxis_55b0390f-0110-46f2-92db-02a302038064" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_PhysicalCommoditiesInventoryDomain_55b0390f-0110-46f2-92db-02a302038064_default" xlink:href="intl-20230630.xsd#intl_PhysicalCommoditiesInventoryDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_intl_PhysicalCommoditiesInventoryAxis_55b0390f-0110-46f2-92db-02a302038064" xlink:to="loc_intl_PhysicalCommoditiesInventoryDomain_55b0390f-0110-46f2-92db-02a302038064_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_PhysicalCommoditiesInventoryDomain_c2ee957a-82c0-4aad-909a-421284462b61" xlink:href="intl-20230630.xsd#intl_PhysicalCommoditiesInventoryDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_intl_PhysicalCommoditiesInventoryAxis_55b0390f-0110-46f2-92db-02a302038064" xlink:to="loc_intl_PhysicalCommoditiesInventoryDomain_c2ee957a-82c0-4aad-909a-421284462b61" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_PhysicalCommoditiesInventoryPreciousMetalsMember_9d6b3020-9474-4fb8-aecb-e8ca11aa6318" xlink:href="intl-20230630.xsd#intl_PhysicalCommoditiesInventoryPreciousMetalsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_intl_PhysicalCommoditiesInventoryDomain_c2ee957a-82c0-4aad-909a-421284462b61" xlink:to="loc_intl_PhysicalCommoditiesInventoryPreciousMetalsMember_9d6b3020-9474-4fb8-aecb-e8ca11aa6318" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.intlfcstone.com/role/GoodwillGoodwillbySegmentDetails" xlink:type="simple" xlink:href="intl-20230630.xsd#GoodwillGoodwillbySegmentDetails"/>
  <link:definitionLink xlink:role="http://www.intlfcstone.com/role/GoodwillGoodwillbySegmentDetails" xlink:type="extended" id="i7b10d2eb397c4e319b5d820328755a9a_GoodwillGoodwillbySegmentDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillLineItems_fa69b200-81cf-4f09-8d7e-449fbb866e22" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GoodwillLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_46d0b0c9-6bd1-4a8a-8838-6af0f3337831" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_fa69b200-81cf-4f09-8d7e-449fbb866e22" xlink:to="loc_us-gaap_Goodwill_46d0b0c9-6bd1-4a8a-8838-6af0f3337831" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfGoodwillTable_0d5bcc26-c129-46c5-9223-dd723798eaa7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfGoodwillTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GoodwillLineItems_fa69b200-81cf-4f09-8d7e-449fbb866e22" xlink:to="loc_us-gaap_ScheduleOfGoodwillTable_0d5bcc26-c129-46c5-9223-dd723798eaa7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_1f4b5ab0-4a22-482a-893a-f99a1e0a1b16" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_0d5bcc26-c129-46c5-9223-dd723798eaa7" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_1f4b5ab0-4a22-482a-893a-f99a1e0a1b16" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_1f4b5ab0-4a22-482a-893a-f99a1e0a1b16_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_1f4b5ab0-4a22-482a-893a-f99a1e0a1b16" xlink:to="loc_us-gaap_SegmentDomain_1f4b5ab0-4a22-482a-893a-f99a1e0a1b16_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_f3247885-ef8e-42f1-a5fa-ec0852d853ff" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_1f4b5ab0-4a22-482a-893a-f99a1e0a1b16" xlink:to="loc_us-gaap_SegmentDomain_f3247885-ef8e-42f1-a5fa-ec0852d853ff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_CommercialSegmentMember_55203215-d850-441f-891f-31cb46b07185" xlink:href="intl-20230630.xsd#intl_CommercialSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_f3247885-ef8e-42f1-a5fa-ec0852d853ff" xlink:to="loc_intl_CommercialSegmentMember_55203215-d850-441f-891f-31cb46b07185" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_InstitutionalSegmentMember_446c8264-876c-4d14-b7d9-708611327f57" xlink:href="intl-20230630.xsd#intl_InstitutionalSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_f3247885-ef8e-42f1-a5fa-ec0852d853ff" xlink:to="loc_intl_InstitutionalSegmentMember_446c8264-876c-4d14-b7d9-708611327f57" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_RetailSegmentMember_e315d5b8-07ce-462d-8b7a-9770ebbf4f06" xlink:href="intl-20230630.xsd#intl_RetailSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_f3247885-ef8e-42f1-a5fa-ec0852d853ff" xlink:to="loc_intl_RetailSegmentMember_e315d5b8-07ce-462d-8b7a-9770ebbf4f06" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_GlobalPaymentsSegmentMember_f64b8522-f99a-4e91-9985-774607ec2c3a" xlink:href="intl-20230630.xsd#intl_GlobalPaymentsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_f3247885-ef8e-42f1-a5fa-ec0852d853ff" xlink:to="loc_intl_GlobalPaymentsSegmentMember_f64b8522-f99a-4e91-9985-774607ec2c3a" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.intlfcstone.com/role/IntangibleAssetsGrossandNetIntangibleAssetsbyMajorClassDetails" xlink:type="simple" xlink:href="intl-20230630.xsd#IntangibleAssetsGrossandNetIntangibleAssetsbyMajorClassDetails"/>
  <link:definitionLink xlink:role="http://www.intlfcstone.com/role/IntangibleAssetsGrossandNetIntangibleAssetsbyMajorClassDetails" xlink:type="extended" id="idd783ab73a7a4645a7b23f0f9f7a512b_IntangibleAssetsGrossandNetIntangibleAssetsbyMajorClassDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_1fb39c8b-8010-4ded-8adf-23727ef22d46" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedTradeNamesGross_7b4639bc-2c14-40eb-bd6d-87e86ff17e69" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedTradeNamesGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_1fb39c8b-8010-4ded-8adf-23727ef22d46" xlink:to="loc_us-gaap_FiniteLivedTradeNamesGross_7b4639bc-2c14-40eb-bd6d-87e86ff17e69" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedComputerSoftwareGross_16a2609f-b270-4096-a82b-4d872ea8b2d3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CapitalizedComputerSoftwareGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_1fb39c8b-8010-4ded-8adf-23727ef22d46" xlink:to="loc_us-gaap_CapitalizedComputerSoftwareGross_16a2609f-b270-4096-a82b-4d872ea8b2d3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedCustomerListsGross_e2c2ed19-bdbd-4715-9d46-a31311d8cb90" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedCustomerListsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_1fb39c8b-8010-4ded-8adf-23727ef22d46" xlink:to="loc_us-gaap_FiniteLivedCustomerListsGross_e2c2ed19-bdbd-4715-9d46-a31311d8cb90" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_a19c6538-b450-4a38-a31e-7b71fa30a602" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_1fb39c8b-8010-4ded-8adf-23727ef22d46" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_a19c6538-b450-4a38-a31e-7b71fa30a602" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_9fb818bd-35fc-4129-9dbf-b555897935c9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_1fb39c8b-8010-4ded-8adf-23727ef22d46" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_9fb818bd-35fc-4129-9dbf-b555897935c9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_ef25c67c-6e57-4a4e-86c0-528fe717d567" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_1fb39c8b-8010-4ded-8adf-23727ef22d46" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_ef25c67c-6e57-4a4e-86c0-528fe717d567" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedLicenseAgreements_5dd3a13c-579b-4590-8c5e-e57c973871c7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IndefiniteLivedLicenseAgreements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_1fb39c8b-8010-4ded-8adf-23727ef22d46" xlink:to="loc_us-gaap_IndefiniteLivedLicenseAgreements_5dd3a13c-579b-4590-8c5e-e57c973871c7" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_2ae33eb4-831c-46a1-b10d-dad06c0f084a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_1fb39c8b-8010-4ded-8adf-23727ef22d46" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_2ae33eb4-831c-46a1-b10d-dad06c0f084a" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_494d1f19-3463-4e81-9748-d25d2fa9d21a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IntangibleAssetsGrossExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_1fb39c8b-8010-4ded-8adf-23727ef22d46" xlink:to="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_494d1f19-3463-4e81-9748-d25d2fa9d21a" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_044b030a-1b47-4ea5-a254-c826de262253" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_1fb39c8b-8010-4ded-8adf-23727ef22d46" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_044b030a-1b47-4ea5-a254-c826de262253" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_6aba2cf2-46df-42b5-8429-d6b9803daa3f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_1fb39c8b-8010-4ded-8adf-23727ef22d46" xlink:to="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_6aba2cf2-46df-42b5-8429-d6b9803daa3f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_482446c5-bf03-4476-a799-b89574630033" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_6aba2cf2-46df-42b5-8429-d6b9803daa3f" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_482446c5-bf03-4476-a799-b89574630033" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_482446c5-bf03-4476-a799-b89574630033_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_482446c5-bf03-4476-a799-b89574630033" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_482446c5-bf03-4476-a799-b89574630033_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_9c814c07-87f3-4259-a027-cb9aa5b67509" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_482446c5-bf03-4476-a799-b89574630033" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_9c814c07-87f3-4259-a027-cb9aa5b67509" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradeNamesMember_e69eae5c-7ca1-4f04-8908-e8ec29b41202" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_9c814c07-87f3-4259-a027-cb9aa5b67509" xlink:to="loc_us-gaap_TradeNamesMember_e69eae5c-7ca1-4f04-8908-e8ec29b41202" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComputerSoftwareIntangibleAssetMember_ba35529b-c8f5-454d-bd53-176a6e3a3704" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ComputerSoftwareIntangibleAssetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_9c814c07-87f3-4259-a027-cb9aa5b67509" xlink:to="loc_us-gaap_ComputerSoftwareIntangibleAssetMember_ba35529b-c8f5-454d-bd53-176a6e3a3704" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_00fb61bb-842a-4e8c-aa52-2467fbcae9d7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_9c814c07-87f3-4259-a027-cb9aa5b67509" xlink:to="loc_us-gaap_CustomerRelationshipsMember_00fb61bb-842a-4e8c-aa52-2467fbcae9d7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_64764510-dd79-481f-a210-0c96a79c1f7c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_6aba2cf2-46df-42b5-8429-d6b9803daa3f" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_64764510-dd79-481f-a210-0c96a79c1f7c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_64764510-dd79-481f-a210-0c96a79c1f7c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_64764510-dd79-481f-a210-0c96a79c1f7c" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_64764510-dd79-481f-a210-0c96a79c1f7c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_0f5527a8-59fe-44a6-8e46-b32962007aee" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_64764510-dd79-481f-a210-0c96a79c1f7c" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_0f5527a8-59fe-44a6-8e46-b32962007aee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InternetDomainNamesMember_81cd90ec-8329-463a-9e4a-af36dcd11920" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InternetDomainNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_0f5527a8-59fe-44a6-8e46-b32962007aee" xlink:to="loc_us-gaap_InternetDomainNamesMember_81cd90ec-8329-463a-9e4a-af36dcd11920" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LicensingAgreementsMember_51e1534f-c7d0-40d6-93de-067387579e53" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LicensingAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_0f5527a8-59fe-44a6-8e46-b32962007aee" xlink:to="loc_us-gaap_LicensingAgreementsMember_51e1534f-c7d0-40d6-93de-067387579e53" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.intlfcstone.com/role/CreditFacilitiesCreditFacilitiesDetails" xlink:type="simple" xlink:href="intl-20230630.xsd#CreditFacilitiesCreditFacilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.intlfcstone.com/role/CreditFacilitiesCreditFacilitiesDetails" xlink:type="extended" id="i69de2301b7d344b49e6b662b9fa7d70e_CreditFacilitiesCreditFacilitiesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLineItems_4c941158-e35a-4621-a824-94dc6e618828" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_NumberOfCreditFacilities_7d5ab68b-4fd3-457d-8924-cb5c456bd211" xlink:href="intl-20230630.xsd#intl_NumberOfCreditFacilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_4c941158-e35a-4621-a824-94dc6e618828" xlink:to="loc_intl_NumberOfCreditFacilities_7d5ab68b-4fd3-457d-8924-cb5c456bd211" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_MaximumBorrowingCapacityUnderCreditFacilities_25f19173-9954-49c8-a528-6fe911b04b54" xlink:href="intl-20230630.xsd#intl_MaximumBorrowingCapacityUnderCreditFacilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_4c941158-e35a-4621-a824-94dc6e618828" xlink:to="loc_intl_MaximumBorrowingCapacityUnderCreditFacilities_25f19173-9954-49c8-a528-6fe911b04b54" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_75416ea1-1947-4159-abd8-bf6d0b8f8d33" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_4c941158-e35a-4621-a824-94dc6e618828" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_75416ea1-1947-4159-abd8-bf6d0b8f8d33" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesPayableToBank_fb9bc79c-ce05-44d6-9b9c-25fa010affe1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NotesPayableToBank"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_4c941158-e35a-4621-a824-94dc6e618828" xlink:to="loc_us-gaap_NotesPayableToBank_fb9bc79c-ce05-44d6-9b9c-25fa010affe1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtWeightedAverageInterestRate_81771c65-a936-4a1e-ac77-0c75a17be53b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtWeightedAverageInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_4c941158-e35a-4621-a824-94dc6e618828" xlink:to="loc_us-gaap_DebtWeightedAverageInterestRate_81771c65-a936-4a1e-ac77-0c75a17be53b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityTable_8cfb4d88-4d04-48c1-a127-0deb17cd7692" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_4c941158-e35a-4621-a824-94dc6e618828" xlink:to="loc_us-gaap_LineOfCreditFacilityTable_8cfb4d88-4d04-48c1-a127-0deb17cd7692" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_b1a8dee6-0200-47a7-9b2d-286e57d9b197" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_8cfb4d88-4d04-48c1-a127-0deb17cd7692" xlink:to="loc_us-gaap_CreditFacilityAxis_b1a8dee6-0200-47a7-9b2d-286e57d9b197" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_b1a8dee6-0200-47a7-9b2d-286e57d9b197_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_b1a8dee6-0200-47a7-9b2d-286e57d9b197" xlink:to="loc_us-gaap_CreditFacilityDomain_b1a8dee6-0200-47a7-9b2d-286e57d9b197_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_bec94047-0bec-4d09-bf76-3fb53bfdc87e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_b1a8dee6-0200-47a7-9b2d-286e57d9b197" xlink:to="loc_us-gaap_CreditFacilityDomain_bec94047-0bec-4d09-bf76-3fb53bfdc87e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_StoneXIncBankOfAmericaSyndicatedCreditFacilityMember_d1a3b4c9-5345-4e86-aa8a-f549b6dbd46e" xlink:href="intl-20230630.xsd#intl_StoneXIncBankOfAmericaSyndicatedCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_bec94047-0bec-4d09-bf76-3fb53bfdc87e" xlink:to="loc_intl_StoneXIncBankOfAmericaSyndicatedCreditFacilityMember_d1a3b4c9-5345-4e86-aa8a-f549b6dbd46e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_FCSMarginLineOfCreditFacilityMember_d19cfec3-9f46-47a6-92b2-f70749d2e80f" xlink:href="intl-20230630.xsd#intl_FCSMarginLineOfCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_bec94047-0bec-4d09-bf76-3fb53bfdc87e" xlink:to="loc_intl_FCSMarginLineOfCreditFacilityMember_d19cfec3-9f46-47a6-92b2-f70749d2e80f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_FMSSubNoteCommodityLineOfCreditFacilityMember_ca1277ac-f6be-4d5e-b80a-a0c00d2969ca" xlink:href="intl-20230630.xsd#intl_FMSSubNoteCommodityLineOfCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_bec94047-0bec-4d09-bf76-3fb53bfdc87e" xlink:to="loc_intl_FMSSubNoteCommodityLineOfCreditFacilityMember_ca1277ac-f6be-4d5e-b80a-a0c00d2969ca" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_StoneXLtdMember_07e6888c-72c8-4e4c-b7a5-8ff6e9893336" xlink:href="intl-20230630.xsd#intl_StoneXLtdMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_bec94047-0bec-4d09-bf76-3fb53bfdc87e" xlink:to="loc_intl_StoneXLtdMember_07e6888c-72c8-4e4c-b7a5-8ff6e9893336" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.intlfcstone.com/role/CreditFacilitiesSeniorSecuredNotesDetails" xlink:type="simple" xlink:href="intl-20230630.xsd#CreditFacilitiesSeniorSecuredNotesDetails"/>
  <link:definitionLink xlink:role="http://www.intlfcstone.com/role/CreditFacilitiesSeniorSecuredNotesDetails" xlink:type="extended" id="i4cd07e02e3c44ea78a9d85cfe26ce035_CreditFacilitiesSeniorSecuredNotesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLineItems_10ad78d6-7506-47dc-ab2a-ac6a7f59134c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_5a68cb3a-5b65-4232-92b5-cb014cb8b27f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_10ad78d6-7506-47dc-ab2a-ac6a7f59134c" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_5a68cb3a-5b65-4232-92b5-cb014cb8b27f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_4d3e4151-c59f-4888-bfd9-50131d479b95" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_10ad78d6-7506-47dc-ab2a-ac6a7f59134c" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_4d3e4151-c59f-4888-bfd9-50131d479b95" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_DebtInstrumentDiscountRateAtIssuanceOfFaceValue_13c1eecd-4cc1-473a-acb5-45d64e814d70" xlink:href="intl-20230630.xsd#intl_DebtInstrumentDiscountRateAtIssuanceOfFaceValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_10ad78d6-7506-47dc-ab2a-ac6a7f59134c" xlink:to="loc_intl_DebtInstrumentDiscountRateAtIssuanceOfFaceValue_13c1eecd-4cc1-473a-acb5-45d64e814d70" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsGross_fd023583-2358-402f-9886-33b0eb558b98" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredFinanceCostsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_10ad78d6-7506-47dc-ab2a-ac6a7f59134c" xlink:to="loc_us-gaap_DeferredFinanceCostsGross_fd023583-2358-402f-9886-33b0eb558b98" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityTable_8e006bb9-8871-4f56-bdfd-5405bd0b60d1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_10ad78d6-7506-47dc-ab2a-ac6a7f59134c" xlink:to="loc_us-gaap_LineOfCreditFacilityTable_8e006bb9-8871-4f56-bdfd-5405bd0b60d1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_9a761e00-9370-48a4-92e2-c986669d1451" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_8e006bb9-8871-4f56-bdfd-5405bd0b60d1" xlink:to="loc_us-gaap_DebtInstrumentAxis_9a761e00-9370-48a4-92e2-c986669d1451" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_9a761e00-9370-48a4-92e2-c986669d1451_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_9a761e00-9370-48a4-92e2-c986669d1451" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_9a761e00-9370-48a4-92e2-c986669d1451_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_ace852b3-d41e-4290-9ec4-f0663480bb46" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_9a761e00-9370-48a4-92e2-c986669d1451" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_ace852b3-d41e-4290-9ec4-f0663480bb46" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_SeniorNotesDueTwentyTwentyFiveMember_59e528e0-2d4e-4d18-9862-4e909a4d6468" xlink:href="intl-20230630.xsd#intl_SeniorNotesDueTwentyTwentyFiveMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_ace852b3-d41e-4290-9ec4-f0663480bb46" xlink:to="loc_intl_SeniorNotesDueTwentyTwentyFiveMember_59e528e0-2d4e-4d18-9862-4e909a4d6468" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.intlfcstone.com/role/CreditFacilitiesCreditFacilitiesandFinancingBridgeCommitmentDetails" xlink:type="simple" xlink:href="intl-20230630.xsd#CreditFacilitiesCreditFacilitiesandFinancingBridgeCommitmentDetails"/>
  <link:definitionLink xlink:role="http://www.intlfcstone.com/role/CreditFacilitiesCreditFacilitiesandFinancingBridgeCommitmentDetails" xlink:type="extended" id="i372a0a7bf87e46b4a10027f380f2c641_CreditFacilitiesCreditFacilitiesandFinancingBridgeCommitmentDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLineItems_f65c3459-6e4b-4d58-94fa-17fd3e24ed60" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_1527c9b9-404e-4dc5-a498-cede09e07b12" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_f65c3459-6e4b-4d58-94fa-17fd3e24ed60" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_1527c9b9-404e-4dc5-a498-cede09e07b12" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_MaximumBorrowingCapacityUnderCreditFacilities_81704452-cb35-4af8-8c48-1db1458d7bb4" xlink:href="intl-20230630.xsd#intl_MaximumBorrowingCapacityUnderCreditFacilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_f65c3459-6e4b-4d58-94fa-17fd3e24ed60" xlink:to="loc_intl_MaximumBorrowingCapacityUnderCreditFacilities_81704452-cb35-4af8-8c48-1db1458d7bb4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermLineOfCredit_1a378f23-03e9-45c6-b673-8f66fe1dcc2a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermLineOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_f65c3459-6e4b-4d58-94fa-17fd3e24ed60" xlink:to="loc_us-gaap_LongTermLineOfCredit_1a378f23-03e9-45c6-b673-8f66fe1dcc2a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LinesOfCreditCurrent_86a3bccf-488c-4c9d-923c-ee56fa0864e7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LinesOfCreditCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_f65c3459-6e4b-4d58-94fa-17fd3e24ed60" xlink:to="loc_us-gaap_LinesOfCreditCurrent_86a3bccf-488c-4c9d-923c-ee56fa0864e7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_AmountOutstandingOnCommittedCreditFacilities_3931f3fa-19b1-4eca-9ac9-c13d29f933ad" xlink:href="intl-20230630.xsd#intl_AmountOutstandingOnCommittedCreditFacilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_f65c3459-6e4b-4d58-94fa-17fd3e24ed60" xlink:to="loc_intl_AmountOutstandingOnCommittedCreditFacilities_3931f3fa-19b1-4eca-9ac9-c13d29f933ad" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_LinesOfCreditUncommittedFacilities_70a53bb1-1bd4-4112-8835-7d35ada8c7cf" xlink:href="intl-20230630.xsd#intl_LinesOfCreditUncommittedFacilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_f65c3459-6e4b-4d58-94fa-17fd3e24ed60" xlink:to="loc_intl_LinesOfCreditUncommittedFacilities_70a53bb1-1bd4-4112-8835-7d35ada8c7cf" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesPayableToBank_b2a761e0-a781-480a-8e38-37b40d0e3777" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NotesPayableToBank"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_f65c3459-6e4b-4d58-94fa-17fd3e24ed60" xlink:to="loc_us-gaap_NotesPayableToBank_b2a761e0-a781-480a-8e38-37b40d0e3777" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotes_8e29fcb5-c2f7-4113-a868-2502b2a72ffc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SeniorNotes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_f65c3459-6e4b-4d58-94fa-17fd3e24ed60" xlink:to="loc_us-gaap_SeniorNotes_8e29fcb5-c2f7-4113-a868-2502b2a72ffc" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtLongtermAndShorttermCombinedAmount_2dd13b16-9c29-44b3-a2eb-eb711c0c3dc0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtLongtermAndShorttermCombinedAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_f65c3459-6e4b-4d58-94fa-17fd3e24ed60" xlink:to="loc_us-gaap_DebtLongtermAndShorttermCombinedAmount_2dd13b16-9c29-44b3-a2eb-eb711c0c3dc0" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_DebtInstrumentNumberOfLenders_8dec4999-cb86-4d89-bb89-161637378d6e" xlink:href="intl-20230630.xsd#intl_DebtInstrumentNumberOfLenders"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_f65c3459-6e4b-4d58-94fa-17fd3e24ed60" xlink:to="loc_intl_DebtInstrumentNumberOfLenders_8dec4999-cb86-4d89-bb89-161637378d6e" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_20c0b7ed-fa3d-4b0e-84e2-641cb57b1a83" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_f65c3459-6e4b-4d58-94fa-17fd3e24ed60" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_20c0b7ed-fa3d-4b0e-84e2-641cb57b1a83" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityTable_af645c11-313b-4cb0-8b6f-3bfc941af933" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_f65c3459-6e4b-4d58-94fa-17fd3e24ed60" xlink:to="loc_us-gaap_LineOfCreditFacilityTable_af645c11-313b-4cb0-8b6f-3bfc941af933" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_f5995fff-10f0-4ee5-bfab-073a2cfe2d2a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_af645c11-313b-4cb0-8b6f-3bfc941af933" xlink:to="loc_us-gaap_CreditFacilityAxis_f5995fff-10f0-4ee5-bfab-073a2cfe2d2a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_f5995fff-10f0-4ee5-bfab-073a2cfe2d2a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_f5995fff-10f0-4ee5-bfab-073a2cfe2d2a" xlink:to="loc_us-gaap_CreditFacilityDomain_f5995fff-10f0-4ee5-bfab-073a2cfe2d2a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_eb4a1f6f-0e2f-4993-a087-49fb04eab2a4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_f5995fff-10f0-4ee5-bfab-073a2cfe2d2a" xlink:to="loc_us-gaap_CreditFacilityDomain_eb4a1f6f-0e2f-4993-a087-49fb04eab2a4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_StoneXIncBankOfAmericaSyndicatedCreditFacilityMember_d340c474-5edf-4fdb-ab44-06d5105a26ab" xlink:href="intl-20230630.xsd#intl_StoneXIncBankOfAmericaSyndicatedCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_eb4a1f6f-0e2f-4993-a087-49fb04eab2a4" xlink:to="loc_intl_StoneXIncBankOfAmericaSyndicatedCreditFacilityMember_d340c474-5edf-4fdb-ab44-06d5105a26ab" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_FCSMarginLineOfCreditFacilityMember_384d84e3-e284-40a7-977e-d38bc995ba50" xlink:href="intl-20230630.xsd#intl_FCSMarginLineOfCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_eb4a1f6f-0e2f-4993-a087-49fb04eab2a4" xlink:to="loc_intl_FCSMarginLineOfCreditFacilityMember_384d84e3-e284-40a7-977e-d38bc995ba50" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_FMSSubNoteCommodityLineOfCreditFacilityMember_c350467c-e971-4a7a-820e-eba09d7a8db5" xlink:href="intl-20230630.xsd#intl_FMSSubNoteCommodityLineOfCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_eb4a1f6f-0e2f-4993-a087-49fb04eab2a4" xlink:to="loc_intl_FMSSubNoteCommodityLineOfCreditFacilityMember_c350467c-e971-4a7a-820e-eba09d7a8db5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_StoneXLtdMember_fbc6e15d-53ef-4a42-9980-32d97e8aed3d" xlink:href="intl-20230630.xsd#intl_StoneXLtdMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_eb4a1f6f-0e2f-4993-a087-49fb04eab2a4" xlink:to="loc_intl_StoneXLtdMember_fbc6e15d-53ef-4a42-9980-32d97e8aed3d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_2039aff0-2cac-4005-adb0-36059eb8e9e6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_af645c11-313b-4cb0-8b6f-3bfc941af933" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_2039aff0-2cac-4005-adb0-36059eb8e9e6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_2039aff0-2cac-4005-adb0-36059eb8e9e6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_2039aff0-2cac-4005-adb0-36059eb8e9e6" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_2039aff0-2cac-4005-adb0-36059eb8e9e6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_72aedee4-fcb5-4442-9cda-c94e4dd90949" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_2039aff0-2cac-4005-adb0-36059eb8e9e6" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_72aedee4-fcb5-4442-9cda-c94e4dd90949" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_2cfdbdfb-76fe-4a15-8acf-94acab9be1ef" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_72aedee4-fcb5-4442-9cda-c94e4dd90949" xlink:to="loc_us-gaap_SecuredDebtMember_2cfdbdfb-76fe-4a15-8acf-94acab9be1ef" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.intlfcstone.com/role/SecuritiesandCommodityFinancingTransactionsCollateralMaturitiesofGrossObligationsDetails" xlink:type="simple" xlink:href="intl-20230630.xsd#SecuritiesandCommodityFinancingTransactionsCollateralMaturitiesofGrossObligationsDetails"/>
  <link:definitionLink xlink:role="http://www.intlfcstone.com/role/SecuritiesandCommodityFinancingTransactionsCollateralMaturitiesofGrossObligationsDetails" xlink:type="extended" id="i42493af4db5942119e58017d975105cb_SecuritiesandCommodityFinancingTransactionsCollateralMaturitiesofGrossObligationsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseLineItems_3d135786-7b53-46d4-8257-575f64d44169" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsSoldUnderAgreementsToRepurchaseLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuritiesSoldUnderAgreementsToRepurchaseGross_8e6009fb-e0bc-4058-9e7c-2fb07e299070" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuritiesSoldUnderAgreementsToRepurchaseGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseLineItems_3d135786-7b53-46d4-8257-575f64d44169" xlink:to="loc_us-gaap_SecuritiesSoldUnderAgreementsToRepurchaseGross_8e6009fb-e0bc-4058-9e7c-2fb07e299070" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuritiesLoaned_1bc4028b-c689-4937-afa3-42a9baaf33fa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuritiesLoaned"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseLineItems_3d135786-7b53-46d4-8257-575f64d44169" xlink:to="loc_us-gaap_SecuritiesLoaned_1bc4028b-c689-4937-afa3-42a9baaf33fa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CollateralizedFinancings_565ed78d-b3ee-4c81-8fb1-59ee4750b766" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CollateralizedFinancings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseLineItems_3d135786-7b53-46d4-8257-575f64d44169" xlink:to="loc_us-gaap_CollateralizedFinancings_565ed78d-b3ee-4c81-8fb1-59ee4750b766" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAssetsSoldUnderAgreementsToRepurchaseTable_2b03aa57-010c-47e2-b536-34dccc87b7a9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAssetsSoldUnderAgreementsToRepurchaseTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseLineItems_3d135786-7b53-46d4-8257-575f64d44169" xlink:to="loc_us-gaap_ScheduleOfAssetsSoldUnderAgreementsToRepurchaseTable_2b03aa57-010c-47e2-b536-34dccc87b7a9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodsAxis_489a213e-e073-444e-b9f6-5883be25af94" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAssetsSoldUnderAgreementsToRepurchaseTable_2b03aa57-010c-47e2-b536-34dccc87b7a9" xlink:to="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodsAxis_489a213e-e073-444e-b9f6-5883be25af94" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodDomain_489a213e-e073-444e-b9f6-5883be25af94_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodsAxis_489a213e-e073-444e-b9f6-5883be25af94" xlink:to="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodDomain_489a213e-e073-444e-b9f6-5883be25af94_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodDomain_5763a6b5-bfd2-4db2-8c17-2ab665383829" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodsAxis_489a213e-e073-444e-b9f6-5883be25af94" xlink:to="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodDomain_5763a6b5-bfd2-4db2-8c17-2ab665383829" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MaturityOvernightAndOnDemandMember_f5bd836d-a8b4-4f17-9c73-4f55fcef7ff3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MaturityOvernightAndOnDemandMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodDomain_5763a6b5-bfd2-4db2-8c17-2ab665383829" xlink:to="loc_us-gaap_MaturityOvernightAndOnDemandMember_f5bd836d-a8b4-4f17-9c73-4f55fcef7ff3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MaturityUpTo30DaysMember_743bb622-4e2c-4204-baff-6929745a7fe1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MaturityUpTo30DaysMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodDomain_5763a6b5-bfd2-4db2-8c17-2ab665383829" xlink:to="loc_us-gaap_MaturityUpTo30DaysMember_743bb622-4e2c-4204-baff-6929745a7fe1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Maturity30To90DaysMember_a72e5a53-eb06-406d-8cc9-f35378c652b4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Maturity30To90DaysMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodDomain_5763a6b5-bfd2-4db2-8c17-2ab665383829" xlink:to="loc_us-gaap_Maturity30To90DaysMember_a72e5a53-eb06-406d-8cc9-f35378c652b4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MaturityOver90DaysMember_5569c348-d5a6-47ef-b8ca-848cf4eeceae" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MaturityOver90DaysMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodDomain_5763a6b5-bfd2-4db2-8c17-2ab665383829" xlink:to="loc_us-gaap_MaturityOver90DaysMember_5569c348-d5a6-47ef-b8ca-848cf4eeceae" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.intlfcstone.com/role/SecuritiesandCommodityFinancingTransactionsUnderlyingCollateralTypesofGrossObligationsDetails" xlink:type="simple" xlink:href="intl-20230630.xsd#SecuritiesandCommodityFinancingTransactionsUnderlyingCollateralTypesofGrossObligationsDetails"/>
  <link:definitionLink xlink:role="http://www.intlfcstone.com/role/SecuritiesandCommodityFinancingTransactionsUnderlyingCollateralTypesofGrossObligationsDetails" xlink:type="extended" id="i0c8f996460874632a09157115312d5e4_SecuritiesandCommodityFinancingTransactionsUnderlyingCollateralTypesofGrossObligationsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseLineItems_317e0792-eff8-43c5-9e4c-3773bb359c73" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsSoldUnderAgreementsToRepurchaseLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuritiesSoldUnderAgreementsToRepurchaseGross_0e37b382-21c2-4666-b894-d0b2166cb25c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuritiesSoldUnderAgreementsToRepurchaseGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseLineItems_317e0792-eff8-43c5-9e4c-3773bb359c73" xlink:to="loc_us-gaap_SecuritiesSoldUnderAgreementsToRepurchaseGross_0e37b382-21c2-4666-b894-d0b2166cb25c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuritiesLoaned_e89dc4c8-36de-467f-9e62-428886b31d01" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuritiesLoaned"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseLineItems_317e0792-eff8-43c5-9e4c-3773bb359c73" xlink:to="loc_us-gaap_SecuritiesLoaned_e89dc4c8-36de-467f-9e62-428886b31d01" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CollateralizedFinancings_acff8c24-1ee7-4e66-bd2a-f35ed918a545" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CollateralizedFinancings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseLineItems_317e0792-eff8-43c5-9e4c-3773bb359c73" xlink:to="loc_us-gaap_CollateralizedFinancings_acff8c24-1ee7-4e66-bd2a-f35ed918a545" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAssetsSoldUnderAgreementsToRepurchaseTable_84b37b13-f1b5-4fa7-b4ca-1e1e45cf4f79" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAssetsSoldUnderAgreementsToRepurchaseTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseLineItems_317e0792-eff8-43c5-9e4c-3773bb359c73" xlink:to="loc_us-gaap_ScheduleOfAssetsSoldUnderAgreementsToRepurchaseTable_84b37b13-f1b5-4fa7-b4ca-1e1e45cf4f79" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_c2e19af2-0a4a-46d7-b483-7c83bc0e34fb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAssetsSoldUnderAgreementsToRepurchaseTable_84b37b13-f1b5-4fa7-b4ca-1e1e45cf4f79" xlink:to="loc_us-gaap_FinancialInstrumentAxis_c2e19af2-0a4a-46d7-b483-7c83bc0e34fb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_c2e19af2-0a4a-46d7-b483-7c83bc0e34fb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_c2e19af2-0a4a-46d7-b483-7c83bc0e34fb" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_c2e19af2-0a4a-46d7-b483-7c83bc0e34fb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_2821b433-cb72-499d-b78e-daeea31ce98d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_c2e19af2-0a4a-46d7-b483-7c83bc0e34fb" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_2821b433-cb72-499d-b78e-daeea31ce98d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USGovernmentDebtSecuritiesMember_d16ded54-e47c-45f1-9150-aeec0b6fa4bf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_USGovernmentDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_2821b433-cb72-499d-b78e-daeea31ce98d" xlink:to="loc_us-gaap_USGovernmentDebtSecuritiesMember_d16ded54-e47c-45f1-9150-aeec0b6fa4bf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_ec8e0d51-8358-4a31-a90a-dedb0f2fbad1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_USGovernmentAgenciesDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_2821b433-cb72-499d-b78e-daeea31ce98d" xlink:to="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_ec8e0d51-8358-4a31-a90a-dedb0f2fbad1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_bc95e7d8-9889-4f23-91e9-ce9c839de5e4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_2821b433-cb72-499d-b78e-daeea31ce98d" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_bc95e7d8-9889-4f23-91e9-ce9c839de5e4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember_1b8fafcc-36bb-41da-bded-c5ce92072a15" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_2821b433-cb72-499d-b78e-daeea31ce98d" xlink:to="loc_us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember_1b8fafcc-36bb-41da-bded-c5ce92072a15" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignGovernmentDebtMember_da4e65a6-53e4-4870-abec-357b027a9025" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignGovernmentDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_2821b433-cb72-499d-b78e-daeea31ce98d" xlink:to="loc_us-gaap_ForeignGovernmentDebtMember_da4e65a6-53e4-4870-abec-357b027a9025" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateBondSecuritiesMember_d2ab6798-5df6-4347-bc15-b0e86cc2e1ed" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CorporateBondSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_2821b433-cb72-499d-b78e-daeea31ce98d" xlink:to="loc_us-gaap_CorporateBondSecuritiesMember_d2ab6798-5df6-4347-bc15-b0e86cc2e1ed" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesMember_aa934622-ab7e-4d08-a04d-11b0439350bb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquitySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_2821b433-cb72-499d-b78e-daeea31ce98d" xlink:to="loc_us-gaap_EquitySecuritiesMember_aa934622-ab7e-4d08-a04d-11b0439350bb" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.intlfcstone.com/role/SecuritiesandCommodityFinancingTransactionsCarryingValueofCollateralPledgedReceivedandRepledgedDetails" xlink:type="simple" xlink:href="intl-20230630.xsd#SecuritiesandCommodityFinancingTransactionsCarryingValueofCollateralPledgedReceivedandRepledgedDetails"/>
  <link:definitionLink xlink:role="http://www.intlfcstone.com/role/SecuritiesandCommodityFinancingTransactionsCarryingValueofCollateralPledgedReceivedandRepledgedDetails" xlink:type="extended" id="i89c4ac8e9fc844dda4ab3a3d47bd8b16_SecuritiesandCommodityFinancingTransactionsCarryingValueofCollateralPledgedReceivedandRepledgedDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseLineItems_b725b6a3-538e-4dde-8643-a815bb9678ac" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsSoldUnderAgreementsToRepurchaseLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentsOwnedAtFairValue_b27235c2-0682-4e9c-a230-bbffe22cec2a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentsOwnedAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseLineItems_b725b6a3-538e-4dde-8643-a815bb9678ac" xlink:to="loc_us-gaap_FinancialInstrumentsOwnedAtFairValue_b27235c2-0682-4e9c-a230-bbffe22cec2a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueOfSecuritiesReceivedAsCollateralThatCanBeResoldOrRepledged_87fb33da-da2d-45fb-b4d2-0dcb78099d71" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueOfSecuritiesReceivedAsCollateralThatCanBeResoldOrRepledged"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseLineItems_b725b6a3-538e-4dde-8643-a815bb9678ac" xlink:to="loc_us-gaap_FairValueOfSecuritiesReceivedAsCollateralThatCanBeResoldOrRepledged_87fb33da-da2d-45fb-b4d2-0dcb78099d71" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueOfSecuritiesReceivedAsCollateralThatHaveBeenResoldOrRepledged_cab3506f-c90b-40ae-8678-abcf0f610d05" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueOfSecuritiesReceivedAsCollateralThatHaveBeenResoldOrRepledged"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseLineItems_b725b6a3-538e-4dde-8643-a815bb9678ac" xlink:to="loc_us-gaap_FairValueOfSecuritiesReceivedAsCollateralThatHaveBeenResoldOrRepledged_cab3506f-c90b-40ae-8678-abcf0f610d05" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuritiesLoanedFairValueOfCollateral_a102c7c6-cc25-4b68-b218-f2f499a86872" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuritiesLoanedFairValueOfCollateral"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseLineItems_b725b6a3-538e-4dde-8643-a815bb9678ac" xlink:to="loc_us-gaap_SecuritiesLoanedFairValueOfCollateral_a102c7c6-cc25-4b68-b218-f2f499a86872" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAssetsSoldUnderAgreementsToRepurchaseTable_80811ee9-c45d-4715-96be-3f0b6a6e8f5d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAssetsSoldUnderAgreementsToRepurchaseTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AssetsSoldUnderAgreementsToRepurchaseLineItems_b725b6a3-538e-4dde-8643-a815bb9678ac" xlink:to="loc_us-gaap_ScheduleOfAssetsSoldUnderAgreementsToRepurchaseTable_80811ee9-c45d-4715-96be-3f0b6a6e8f5d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeAxis_2d95f0af-573e-4cd1-90e0-2425a94a5906" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAssetsSoldUnderAgreementsToRepurchaseTable_80811ee9-c45d-4715-96be-3f0b6a6e8f5d" xlink:to="loc_us-gaap_InvestmentTypeAxis_2d95f0af-573e-4cd1-90e0-2425a94a5906" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_2d95f0af-573e-4cd1-90e0-2425a94a5906_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InvestmentTypeAxis_2d95f0af-573e-4cd1-90e0-2425a94a5906" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_2d95f0af-573e-4cd1-90e0-2425a94a5906_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_6f352530-c261-4531-9fec-419460d7db53" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InvestmentTypeAxis_2d95f0af-573e-4cd1-90e0-2425a94a5906" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_6f352530-c261-4531-9fec-419460d7db53" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepurchaseAgreementsMember_f741e9d2-19cb-461f-a526-c611e7533ee2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RepurchaseAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_6f352530-c261-4531-9fec-419460d7db53" xlink:to="loc_us-gaap_RepurchaseAgreementsMember_f741e9d2-19cb-461f-a526-c611e7533ee2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgedStatusAxis_16148d82-5302-4e38-a05f-f3dab4c358ab" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PledgedStatusAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAssetsSoldUnderAgreementsToRepurchaseTable_80811ee9-c45d-4715-96be-3f0b6a6e8f5d" xlink:to="loc_us-gaap_PledgedStatusAxis_16148d82-5302-4e38-a05f-f3dab4c358ab" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgedStatusDomain_16148d82-5302-4e38-a05f-f3dab4c358ab_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PledgedStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PledgedStatusAxis_16148d82-5302-4e38-a05f-f3dab4c358ab" xlink:to="loc_us-gaap_PledgedStatusDomain_16148d82-5302-4e38-a05f-f3dab4c358ab_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgedStatusDomain_96c7a78e-1b9a-434d-9635-db7d9db0d724" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PledgedStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PledgedStatusAxis_16148d82-5302-4e38-a05f-f3dab4c358ab" xlink:to="loc_us-gaap_PledgedStatusDomain_96c7a78e-1b9a-434d-9635-db7d9db0d724" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetPledgedAsCollateralWithoutRightMember_78d99292-3bc7-476c-abaf-1aca07344aa8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetPledgedAsCollateralWithoutRightMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PledgedStatusDomain_96c7a78e-1b9a-434d-9635-db7d9db0d724" xlink:to="loc_us-gaap_AssetPledgedAsCollateralWithoutRightMember_78d99292-3bc7-476c-abaf-1aca07344aa8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetPledgedAsCollateralWithRightMember_758ffc83-5261-4197-9e7c-91b5ce3dcfa6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetPledgedAsCollateralWithRightMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PledgedStatusDomain_96c7a78e-1b9a-434d-9635-db7d9db0d724" xlink:to="loc_us-gaap_AssetPledgedAsCollateralWithRightMember_758ffc83-5261-4197-9e7c-91b5ce3dcfa6" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.intlfcstone.com/role/CommitmentsandContingenciesDetails" xlink:type="simple" xlink:href="intl-20230630.xsd#CommitmentsandContingenciesDetails"/>
  <link:definitionLink xlink:role="http://www.intlfcstone.com/role/CommitmentsandContingenciesDetails" xlink:type="extended" id="i36c4d94cf933493d8956877df57db6a7_CommitmentsandContingenciesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesLineItems_84908050-c390-4d7d-a9ae-494bae49bb50" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LossContingenciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_NumberOfAccounts_c1b85a1a-e5a7-4eb5-bb0d-f51387342dc8" xlink:href="intl-20230630.xsd#intl_NumberOfAccounts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_84908050-c390-4d7d-a9ae-494bae49bb50" xlink:to="loc_intl_NumberOfAccounts_c1b85a1a-e5a7-4eb5-bb0d-f51387342dc8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyEstimateOfPossibleLoss_15816b8e-5331-427a-bab6-4e05455ec4cb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LossContingencyEstimateOfPossibleLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_84908050-c390-4d7d-a9ae-494bae49bb50" xlink:to="loc_us-gaap_LossContingencyEstimateOfPossibleLoss_15816b8e-5331-427a-bab6-4e05455ec4cb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_LossContingencyIndividualAccountsMaximumReceivable_6ccc8c66-273f-45e9-8201-c6c2560aa07a" xlink:href="intl-20230630.xsd#intl_LossContingencyIndividualAccountsMaximumReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_84908050-c390-4d7d-a9ae-494bae49bb50" xlink:to="loc_intl_LossContingencyIndividualAccountsMaximumReceivable_6ccc8c66-273f-45e9-8201-c6c2560aa07a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyAccrualAtCarryingValue_c62125bf-e7b2-4e8f-babb-0e0fece7c49d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LossContingencyAccrualAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_84908050-c390-4d7d-a9ae-494bae49bb50" xlink:to="loc_us-gaap_LossContingencyAccrualAtCarryingValue_c62125bf-e7b2-4e8f-babb-0e0fece7c49d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SelfInsuranceReserve_4155470a-48a4-4ab3-9111-45fc81de15e6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SelfInsuranceReserve"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_84908050-c390-4d7d-a9ae-494bae49bb50" xlink:to="loc_us-gaap_SelfInsuranceReserve_4155470a-48a4-4ab3-9111-45fc81de15e6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesTable_321cd4d8-3854-4124-bcb5-60e2b823c748" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LossContingenciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LossContingenciesLineItems_84908050-c390-4d7d-a9ae-494bae49bb50" xlink:to="loc_us-gaap_LossContingenciesTable_321cd4d8-3854-4124-bcb5-60e2b823c748" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_928b553f-b5db-46d8-93e4-0cca0fbf685a" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_321cd4d8-3854-4124-bcb5-60e2b823c748" xlink:to="loc_dei_LegalEntityAxis_928b553f-b5db-46d8-93e4-0cca0fbf685a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_928b553f-b5db-46d8-93e4-0cca0fbf685a_default" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_928b553f-b5db-46d8-93e4-0cca0fbf685a" xlink:to="loc_dei_EntityDomain_928b553f-b5db-46d8-93e4-0cca0fbf685a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_48952717-08cf-45ef-9b78-e7e950811cb0" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_928b553f-b5db-46d8-93e4-0cca0fbf685a" xlink:to="loc_dei_EntityDomain_48952717-08cf-45ef-9b78-e7e950811cb0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_StoneXFinancialMember_7fcc371f-79ff-4e6b-a18f-66a8027c9675" xlink:href="intl-20230630.xsd#intl_StoneXFinancialMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_48952717-08cf-45ef-9b78-e7e950811cb0" xlink:to="loc_intl_StoneXFinancialMember_7fcc371f-79ff-4e6b-a18f-66a8027c9675" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.intlfcstone.com/role/AccumulatedOtherComprehensiveLossNetDetails" xlink:type="simple" xlink:href="intl-20230630.xsd#AccumulatedOtherComprehensiveLossNetDetails"/>
  <link:definitionLink xlink:role="http://www.intlfcstone.com/role/AccumulatedOtherComprehensiveLossNetDetails" xlink:type="extended" id="i36a361c201ba4d6f89ce23c9ef9230a0_AccumulatedOtherComprehensiveLossNetDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_aaa987b2-d55c-4e84-9899-5eb05ce90381" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_e5d2419a-27e8-425a-b8c9-0b7386b1d475" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AOCIAttributableToParentNetOfTaxRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_aaa987b2-d55c-4e84-9899-5eb05ce90381" xlink:to="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_e5d2419a-27e8-425a-b8c9-0b7386b1d475" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_ae6fb98f-75be-4fcf-a6da-3bb2353e22a1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_e5d2419a-27e8-425a-b8c9-0b7386b1d475" xlink:to="loc_us-gaap_StockholdersEquity_ae6fb98f-75be-4fcf-a6da-3bb2353e22a1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_a7e7a1fd-26cf-47a5-a7cf-9b8bd4e17dc9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_e5d2419a-27e8-425a-b8c9-0b7386b1d475" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_a7e7a1fd-26cf-47a5-a7cf-9b8bd4e17dc9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_e67254aa-cc7c-4cde-ac7f-57b2ab44b9ec" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_961d758a-c342-4368-ad9a-4ab2b164c700" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_aaa987b2-d55c-4e84-9899-5eb05ce90381" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_961d758a-c342-4368-ad9a-4ab2b164c700" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_99c37201-d392-4872-aecf-8c91e78f3ec6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_961d758a-c342-4368-ad9a-4ab2b164c700" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_99c37201-d392-4872-aecf-8c91e78f3ec6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_99c37201-d392-4872-aecf-8c91e78f3ec6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_99c37201-d392-4872-aecf-8c91e78f3ec6" xlink:to="loc_us-gaap_EquityComponentDomain_99c37201-d392-4872-aecf-8c91e78f3ec6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_d265cda6-d82e-4f87-9b04-17a33611aa67" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_99c37201-d392-4872-aecf-8c91e78f3ec6" xlink:to="loc_us-gaap_EquityComponentDomain_d265cda6-d82e-4f87-9b04-17a33611aa67" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedTranslationAdjustmentMember_67e698cf-3d11-47d5-9bd7-83c1b2012536" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedTranslationAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_d265cda6-d82e-4f87-9b04-17a33611aa67" xlink:to="loc_us-gaap_AccumulatedTranslationAdjustmentMember_67e698cf-3d11-47d5-9bd7-83c1b2012536" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_e2b29547-4845-45d4-a356-39b8b9b8bc59" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_d265cda6-d82e-4f87-9b04-17a33611aa67" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_e2b29547-4845-45d4-a356-39b8b9b8bc59" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_75ccde74-5167-453e-bfb4-b0da7723747f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_d265cda6-d82e-4f87-9b04-17a33611aa67" xlink:to="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_75ccde74-5167-453e-bfb4-b0da7723747f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_834369c2-26f3-4f00-902a-3a4bcbd6e87d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_d265cda6-d82e-4f87-9b04-17a33611aa67" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_834369c2-26f3-4f00-902a-3a4bcbd6e87d" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.intlfcstone.com/role/RevenuefromContractswithClientsRevenuefromContractswithClientsDetails" xlink:type="simple" xlink:href="intl-20230630.xsd#RevenuefromContractswithClientsRevenuefromContractswithClientsDetails"/>
  <link:definitionLink xlink:role="http://www.intlfcstone.com/role/RevenuefromContractswithClientsRevenuefromContractswithClientsDetails" xlink:type="extended" id="ib7cd67186b6a40bdaee3a35ecd147ccf_RevenuefromContractswithClientsRevenuefromContractswithClientsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_1451e565-79d4-42fd-8e26-bf1d551e6801" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_9f6120c0-2748-46a7-8453-6e4ccd474684" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_1451e565-79d4-42fd-8e26-bf1d551e6801" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_9f6120c0-2748-46a7-8453-6e4ccd474684" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_bd0640cb-9466-41cc-95b8-1553203ebc95" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_1451e565-79d4-42fd-8e26-bf1d551e6801" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_bd0640cb-9466-41cc-95b8-1553203ebc95" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueNotFromContractWithCustomer_64b9a25b-7661-42ce-b296-c4bdd73dbe5a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueNotFromContractWithCustomer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_1451e565-79d4-42fd-8e26-bf1d551e6801" xlink:to="loc_us-gaap_RevenueNotFromContractWithCustomer_64b9a25b-7661-42ce-b296-c4bdd73dbe5a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrincipalInvestmentGainsLosses_73c9fd6a-7173-4f35-8a45-220a9f33b701" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PrincipalInvestmentGainsLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_1451e565-79d4-42fd-8e26-bf1d551e6801" xlink:to="loc_us-gaap_PrincipalInvestmentGainsLosses_73c9fd6a-7173-4f35-8a45-220a9f33b701" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeOperating_7d450c5a-2865-45e0-bd36-928b86c84ffd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestIncomeOperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_1451e565-79d4-42fd-8e26-bf1d551e6801" xlink:to="loc_us-gaap_InterestIncomeOperating_7d450c5a-2865-45e0-bd36-928b86c84ffd" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_a1bf1c35-6365-4b95-aeb2-ed4d9154506a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_1451e565-79d4-42fd-8e26-bf1d551e6801" xlink:to="loc_us-gaap_Revenues_a1bf1c35-6365-4b95-aeb2-ed4d9154506a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossProfit_229a56b5-1fb2-4372-a0a5-bb41d8198f2a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GrossProfit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_1451e565-79d4-42fd-8e26-bf1d551e6801" xlink:to="loc_us-gaap_GrossProfit_229a56b5-1fb2-4372-a0a5-bb41d8198f2a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_f910fe11-616a-42c7-bb5f-a21b5b7a3ff6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_1451e565-79d4-42fd-8e26-bf1d551e6801" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_f910fe11-616a-42c7-bb5f-a21b5b7a3ff6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_0d34be99-6ddc-4d1d-a006-cae8ce660ce4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_f910fe11-616a-42c7-bb5f-a21b5b7a3ff6" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_0d34be99-6ddc-4d1d-a006-cae8ce660ce4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_0d34be99-6ddc-4d1d-a006-cae8ce660ce4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_0d34be99-6ddc-4d1d-a006-cae8ce660ce4" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_0d34be99-6ddc-4d1d-a006-cae8ce660ce4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_27e9cbab-80b3-4e10-ab56-3207fd863e45" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_0d34be99-6ddc-4d1d-a006-cae8ce660ce4" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_27e9cbab-80b3-4e10-ab56-3207fd863e45" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerMember_bf37e415-62a2-4b75-b04c-07695d26621b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueFromContractWithCustomerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_27e9cbab-80b3-4e10-ab56-3207fd863e45" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerMember_bf37e415-62a2-4b75-b04c-07695d26621b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_82e599b0-38a5-4b7f-9d86-eda8fb4fd3e4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_f910fe11-616a-42c7-bb5f-a21b5b7a3ff6" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_82e599b0-38a5-4b7f-9d86-eda8fb4fd3e4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_82e599b0-38a5-4b7f-9d86-eda8fb4fd3e4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_82e599b0-38a5-4b7f-9d86-eda8fb4fd3e4" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_82e599b0-38a5-4b7f-9d86-eda8fb4fd3e4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_a1aaea4e-742a-451c-ab5e-66be860a912c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_82e599b0-38a5-4b7f-9d86-eda8fb4fd3e4" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_a1aaea4e-742a-451c-ab5e-66be860a912c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_5800d923-7745-482e-8295-0c4d2a0f1f93" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CustomerConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_a1aaea4e-742a-451c-ab5e-66be860a912c" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_5800d923-7745-482e-8295-0c4d2a0f1f93" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MajorCustomersAxis_f33fa65e-9a69-4010-b3d5-05227840a442" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MajorCustomersAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_f910fe11-616a-42c7-bb5f-a21b5b7a3ff6" xlink:to="loc_srt_MajorCustomersAxis_f33fa65e-9a69-4010-b3d5-05227840a442" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_f33fa65e-9a69-4010-b3d5-05227840a442_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_f33fa65e-9a69-4010-b3d5-05227840a442" xlink:to="loc_srt_NameOfMajorCustomerDomain_f33fa65e-9a69-4010-b3d5-05227840a442_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_3187f2b3-57b4-499b-9be3-bcccf9842c66" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_f33fa65e-9a69-4010-b3d5-05227840a442" xlink:to="loc_srt_NameOfMajorCustomerDomain_3187f2b3-57b4-499b-9be3-bcccf9842c66" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_ClientsMember_a4da7b2f-c63d-4b9d-9cac-8eeae0614acc" xlink:href="intl-20230630.xsd#intl_ClientsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_3187f2b3-57b4-499b-9be3-bcccf9842c66" xlink:to="loc_intl_ClientsMember_a4da7b2f-c63d-4b9d-9cac-8eeae0614acc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_ec1546bf-8c05-4509-9949-e63fd4724218" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_f910fe11-616a-42c7-bb5f-a21b5b7a3ff6" xlink:to="loc_srt_ProductOrServiceAxis_ec1546bf-8c05-4509-9949-e63fd4724218" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_ec1546bf-8c05-4509-9949-e63fd4724218_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_ec1546bf-8c05-4509-9949-e63fd4724218" xlink:to="loc_srt_ProductsAndServicesDomain_ec1546bf-8c05-4509-9949-e63fd4724218_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_05b9d177-0b80-4399-90ac-623ab25c2691" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_ec1546bf-8c05-4509-9949-e63fd4724218" xlink:to="loc_srt_ProductsAndServicesDomain_05b9d177-0b80-4399-90ac-623ab25c2691" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_ExchangeTradedFuturesAndOptionsMember_6dff0975-0845-4665-bd15-e7a168107f0a" xlink:href="intl-20230630.xsd#intl_ExchangeTradedFuturesAndOptionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_05b9d177-0b80-4399-90ac-623ab25c2691" xlink:to="loc_intl_ExchangeTradedFuturesAndOptionsMember_6dff0975-0845-4665-bd15-e7a168107f0a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_OTCDerivativeBrokerageMember_6763b6ca-28f3-4f3d-a764-545ddf74f180" xlink:href="intl-20230630.xsd#intl_OTCDerivativeBrokerageMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_05b9d177-0b80-4399-90ac-623ab25c2691" xlink:to="loc_intl_OTCDerivativeBrokerageMember_6763b6ca-28f3-4f3d-a764-545ddf74f180" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_EquitiesandFixedIncomeCommissionsMember_ae0bf846-bfe8-499a-bf5b-245ea481f891" xlink:href="intl-20230630.xsd#intl_EquitiesandFixedIncomeCommissionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_05b9d177-0b80-4399-90ac-623ab25c2691" xlink:to="loc_intl_EquitiesandFixedIncomeCommissionsMember_ae0bf846-bfe8-499a-bf5b-245ea481f891" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_MutualFundSalesBasedCommissionsMember_0c2ec90b-305d-4826-ac33-051cfbbaeb90" xlink:href="intl-20230630.xsd#intl_MutualFundSalesBasedCommissionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_05b9d177-0b80-4399-90ac-623ab25c2691" xlink:to="loc_intl_MutualFundSalesBasedCommissionsMember_0c2ec90b-305d-4826-ac33-051cfbbaeb90" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableAnnuityMember_36658742-b217-4b02-98ce-d7627f8ad694" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VariableAnnuityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_05b9d177-0b80-4399-90ac-623ab25c2691" xlink:to="loc_us-gaap_VariableAnnuityMember_36658742-b217-4b02-98ce-d7627f8ad694" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_OtherSalesBasedCommissionsMember_11168a8d-8c91-4f00-bebf-8bc764b2e6b1" xlink:href="intl-20230630.xsd#intl_OtherSalesBasedCommissionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_05b9d177-0b80-4399-90ac-623ab25c2691" xlink:to="loc_intl_OtherSalesBasedCommissionsMember_11168a8d-8c91-4f00-bebf-8bc764b2e6b1" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_SalesBasedCommissionsMember_11ae121c-af39-4e49-9855-2916edd61f84" xlink:href="intl-20230630.xsd#intl_SalesBasedCommissionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_05b9d177-0b80-4399-90ac-623ab25c2691" xlink:to="loc_intl_SalesBasedCommissionsMember_11ae121c-af39-4e49-9855-2916edd61f84" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_MutualFundTrailingCommissionsMember_740378c9-91a2-406b-93f6-ee84db48fa96" xlink:href="intl-20230630.xsd#intl_MutualFundTrailingCommissionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_05b9d177-0b80-4399-90ac-623ab25c2691" xlink:to="loc_intl_MutualFundTrailingCommissionsMember_740378c9-91a2-406b-93f6-ee84db48fa96" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_InsuranceAnnuityTrailingCommissionsMember_68eba598-ce21-4c4e-a5d6-da03b9cf4afd" xlink:href="intl-20230630.xsd#intl_InsuranceAnnuityTrailingCommissionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_05b9d177-0b80-4399-90ac-623ab25c2691" xlink:to="loc_intl_InsuranceAnnuityTrailingCommissionsMember_68eba598-ce21-4c4e-a5d6-da03b9cf4afd" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_TrailingCommissionsMember_e8e9d8d0-931c-4dfc-b97c-64e5b1c4f88a" xlink:href="intl-20230630.xsd#intl_TrailingCommissionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_05b9d177-0b80-4399-90ac-623ab25c2691" xlink:to="loc_intl_TrailingCommissionsMember_e8e9d8d0-931c-4dfc-b97c-64e5b1c4f88a" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClearingServiceMember_c2f95af4-0b59-4332-8504-28bf7d4a32c8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClearingServiceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_05b9d177-0b80-4399-90ac-623ab25c2691" xlink:to="loc_us-gaap_ClearingServiceMember_c2f95af4-0b59-4332-8504-28bf7d4a32c8" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_TradeConversionFeesMember_28a386f1-f2b3-4d54-b555-37fdf5eec722" xlink:href="intl-20230630.xsd#intl_TradeConversionFeesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_05b9d177-0b80-4399-90ac-623ab25c2691" xlink:to="loc_intl_TradeConversionFeesMember_28a386f1-f2b3-4d54-b555-37fdf5eec722" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_OtherCommissionAndClearingFeesMember_1f92ab9a-6183-4405-8d9c-5ed5c4e06875" xlink:href="intl-20230630.xsd#intl_OtherCommissionAndClearingFeesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_05b9d177-0b80-4399-90ac-623ab25c2691" xlink:to="loc_intl_OtherCommissionAndClearingFeesMember_1f92ab9a-6183-4405-8d9c-5ed5c4e06875" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_CommissionandClearingFeesMember_f0b33014-ee55-4398-9587-b152e82fc2fd" xlink:href="intl-20230630.xsd#intl_CommissionandClearingFeesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_05b9d177-0b80-4399-90ac-623ab25c2691" xlink:to="loc_intl_CommissionandClearingFeesMember_f0b33014-ee55-4398-9587-b152e82fc2fd" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_UnderwritingFeesMember_4295bf94-b53a-4bcf-9c25-ac2650c9e1d2" xlink:href="intl-20230630.xsd#intl_UnderwritingFeesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_05b9d177-0b80-4399-90ac-623ab25c2691" xlink:to="loc_intl_UnderwritingFeesMember_4295bf94-b53a-4bcf-9c25-ac2650c9e1d2" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetManagement1Member_dda381af-888b-495c-9e25-4157cc293aef" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetManagement1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_05b9d177-0b80-4399-90ac-623ab25c2691" xlink:to="loc_us-gaap_AssetManagement1Member_dda381af-888b-495c-9e25-4157cc293aef" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_AdvisoryandConsultingFeesMember_df41b1df-f595-4fe7-8cc3-b174134ad86d" xlink:href="intl-20230630.xsd#intl_AdvisoryandConsultingFeesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_05b9d177-0b80-4399-90ac-623ab25c2691" xlink:to="loc_intl_AdvisoryandConsultingFeesMember_df41b1df-f595-4fe7-8cc3-b174134ad86d" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_SweepProgramFeesMember_cc2e7a28-04ab-4b22-b6c3-1666923ae409" xlink:href="intl-20230630.xsd#intl_SweepProgramFeesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_05b9d177-0b80-4399-90ac-623ab25c2691" xlink:to="loc_intl_SweepProgramFeesMember_cc2e7a28-04ab-4b22-b6c3-1666923ae409" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_ClientAccountFeesMember_dc1be9a8-829d-42ca-9c2f-1f3f12433501" xlink:href="intl-20230630.xsd#intl_ClientAccountFeesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_05b9d177-0b80-4399-90ac-623ab25c2691" xlink:to="loc_intl_ClientAccountFeesMember_dc1be9a8-829d-42ca-9c2f-1f3f12433501" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_OtherConsultingManagementandAccountFeesMember_f891af14-eba8-4c49-9b08-712fa4dc9036" xlink:href="intl-20230630.xsd#intl_OtherConsultingManagementandAccountFeesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_05b9d177-0b80-4399-90ac-623ab25c2691" xlink:to="loc_intl_OtherConsultingManagementandAccountFeesMember_f891af14-eba8-4c49-9b08-712fa4dc9036" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_ConsultingManagementAndAccountFeesMember_e801bf2b-3ce4-4d2b-9b77-a4f28ed9b678" xlink:href="intl-20230630.xsd#intl_ConsultingManagementAndAccountFeesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_05b9d177-0b80-4399-90ac-623ab25c2691" xlink:to="loc_intl_ConsultingManagementAndAccountFeesMember_e801bf2b-3ce4-4d2b-9b77-a4f28ed9b678" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_PreciousMetalsRetailSalesMember_08dc2bae-55c5-4464-9016-9a9d67b3e253" xlink:href="intl-20230630.xsd#intl_PreciousMetalsRetailSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_05b9d177-0b80-4399-90ac-623ab25c2691" xlink:to="loc_intl_PreciousMetalsRetailSalesMember_08dc2bae-55c5-4464-9016-9a9d67b3e253" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_PreciousMetalsTradingMember_cfca718a-87d6-4b2e-aa5e-973c6af9ff23" xlink:href="intl-20230630.xsd#intl_PreciousMetalsTradingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_05b9d177-0b80-4399-90ac-623ab25c2691" xlink:to="loc_intl_PreciousMetalsTradingMember_cfca718a-87d6-4b2e-aa5e-973c6af9ff23" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_AgriculturalAndEnergyProductTradingMember_59e29180-a5e8-42ac-acd7-221715b0fff8" xlink:href="intl-20230630.xsd#intl_AgriculturalAndEnergyProductTradingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_05b9d177-0b80-4399-90ac-623ab25c2691" xlink:to="loc_intl_AgriculturalAndEnergyProductTradingMember_59e29180-a5e8-42ac-acd7-221715b0fff8" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TimingOfTransferOfGoodOrServiceAxis_d0fd1bb5-14bf-439e-8015-ac9a01f70129" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TimingOfTransferOfGoodOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_f910fe11-616a-42c7-bb5f-a21b5b7a3ff6" xlink:to="loc_us-gaap_TimingOfTransferOfGoodOrServiceAxis_d0fd1bb5-14bf-439e-8015-ac9a01f70129" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_d0fd1bb5-14bf-439e-8015-ac9a01f70129_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TimingOfTransferOfGoodOrServiceDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TimingOfTransferOfGoodOrServiceAxis_d0fd1bb5-14bf-439e-8015-ac9a01f70129" xlink:to="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_d0fd1bb5-14bf-439e-8015-ac9a01f70129_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_b926948e-bf25-43e8-be39-b97fa08590bf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TimingOfTransferOfGoodOrServiceDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TimingOfTransferOfGoodOrServiceAxis_d0fd1bb5-14bf-439e-8015-ac9a01f70129" xlink:to="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_b926948e-bf25-43e8-be39-b97fa08590bf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransferredAtPointInTimeMember_450e100a-74bc-4fd6-969d-66454cadd249" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransferredAtPointInTimeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_b926948e-bf25-43e8-be39-b97fa08590bf" xlink:to="loc_us-gaap_TransferredAtPointInTimeMember_450e100a-74bc-4fd6-969d-66454cadd249" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransferredOverTimeMember_d1bc04ca-83af-458f-b312-3cd45276558d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransferredOverTimeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_b926948e-bf25-43e8-be39-b97fa08590bf" xlink:to="loc_us-gaap_TransferredOverTimeMember_d1bc04ca-83af-458f-b312-3cd45276558d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_eaa75534-f626-48d9-824b-1d0344a97de1" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_f910fe11-616a-42c7-bb5f-a21b5b7a3ff6" xlink:to="loc_srt_StatementGeographicalAxis_eaa75534-f626-48d9-824b-1d0344a97de1" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_eaa75534-f626-48d9-824b-1d0344a97de1_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_eaa75534-f626-48d9-824b-1d0344a97de1" xlink:to="loc_srt_SegmentGeographicalDomain_eaa75534-f626-48d9-824b-1d0344a97de1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_630fc22d-f0f9-48fb-8a55-69a93a25cd2b" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_eaa75534-f626-48d9-824b-1d0344a97de1" xlink:to="loc_srt_SegmentGeographicalDomain_630fc22d-f0f9-48fb-8a55-69a93a25cd2b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_b400c292-8d0f-4685-b2e0-b0de7d53a0cb" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_630fc22d-f0f9-48fb-8a55-69a93a25cd2b" xlink:to="loc_country_US_b400c292-8d0f-4685-b2e0-b0de7d53a0cb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EuropeMember_a4ea410c-c94c-4951-9fec-dd76c2b918ee" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_EuropeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_630fc22d-f0f9-48fb-8a55-69a93a25cd2b" xlink:to="loc_srt_EuropeMember_a4ea410c-c94c-4951-9fec-dd76c2b918ee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SouthAmericaMember_6ba6f5f1-f4ee-4f22-81cb-1b10ee5c6ec7" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SouthAmericaMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_630fc22d-f0f9-48fb-8a55-69a93a25cd2b" xlink:to="loc_srt_SouthAmericaMember_6ba6f5f1-f4ee-4f22-81cb-1b10ee5c6ec7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_MiddleEastAndAsiaMember_f4a6bc65-0bbc-45cc-a01a-d05097befd15" xlink:href="intl-20230630.xsd#intl_MiddleEastAndAsiaMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_630fc22d-f0f9-48fb-8a55-69a93a25cd2b" xlink:to="loc_intl_MiddleEastAndAsiaMember_f4a6bc65-0bbc-45cc-a01a-d05097befd15" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_OtherCountryNotMentionedAboveMember_6c0cc01c-d7ff-4992-b504-7a31cca35d52" xlink:href="intl-20230630.xsd#intl_OtherCountryNotMentionedAboveMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_630fc22d-f0f9-48fb-8a55-69a93a25cd2b" xlink:to="loc_intl_OtherCountryNotMentionedAboveMember_6c0cc01c-d7ff-4992-b504-7a31cca35d52" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.intlfcstone.com/role/RevenuefromContractswithClientsScheduleofPrincipalGainsNetRelatedToIncomeandExpenseofDividendsDetails" xlink:type="simple" xlink:href="intl-20230630.xsd#RevenuefromContractswithClientsScheduleofPrincipalGainsNetRelatedToIncomeandExpenseofDividendsDetails"/>
  <link:definitionLink xlink:role="http://www.intlfcstone.com/role/RevenuefromContractswithClientsScheduleofPrincipalGainsNetRelatedToIncomeandExpenseofDividendsDetails" xlink:type="extended" id="i6e4bdb3a347c47b1abe671a7cbccf446_RevenuefromContractswithClientsScheduleofPrincipalGainsNetRelatedToIncomeandExpenseofDividendsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_d67b4416-db4b-4d77-b35f-c4d755ef615c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_DividendIncomeExpenseNet_d381f788-5e02-486f-8e94-9579149cc526" xlink:href="intl-20230630.xsd#intl_DividendIncomeExpenseNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_d67b4416-db4b-4d77-b35f-c4d755ef615c" xlink:to="loc_intl_DividendIncomeExpenseNet_d381f788-5e02-486f-8e94-9579149cc526" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_95ec24f3-a9dd-45ee-bd11-3188cdd440dc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_d67b4416-db4b-4d77-b35f-c4d755ef615c" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_95ec24f3-a9dd-45ee-bd11-3188cdd440dc" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_6ef189db-7007-464d-9186-d2b05886d693" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_95ec24f3-a9dd-45ee-bd11-3188cdd440dc" xlink:to="loc_us-gaap_FinancialInstrumentAxis_6ef189db-7007-464d-9186-d2b05886d693" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_6ef189db-7007-464d-9186-d2b05886d693_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_6ef189db-7007-464d-9186-d2b05886d693" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_6ef189db-7007-464d-9186-d2b05886d693_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_02d4b795-6716-4dbc-bf6a-e44c1bade80e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_6ef189db-7007-464d-9186-d2b05886d693" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_02d4b795-6716-4dbc-bf6a-e44c1bade80e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesMember_e1cd792a-00f2-47b1-9ba1-8369176c3d99" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquitySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_02d4b795-6716-4dbc-bf6a-e44c1bade80e" xlink:to="loc_us-gaap_EquitySecuritiesMember_e1cd792a-00f2-47b1-9ba1-8369176c3d99" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PositionAxis_a3a2d524-66fd-41ce-ba88-1ab96f8de47e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PositionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_95ec24f3-a9dd-45ee-bd11-3188cdd440dc" xlink:to="loc_us-gaap_PositionAxis_a3a2d524-66fd-41ce-ba88-1ab96f8de47e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PositionDomain_a3a2d524-66fd-41ce-ba88-1ab96f8de47e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PositionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PositionAxis_a3a2d524-66fd-41ce-ba88-1ab96f8de47e" xlink:to="loc_us-gaap_PositionDomain_a3a2d524-66fd-41ce-ba88-1ab96f8de47e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PositionDomain_f4b6f33b-7991-4384-acfb-7cee8e727adb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PositionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PositionAxis_a3a2d524-66fd-41ce-ba88-1ab96f8de47e" xlink:to="loc_us-gaap_PositionDomain_f4b6f33b-7991-4384-acfb-7cee8e727adb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongMember_8d09624f-24a0-4e0f-b012-058075fa720a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PositionDomain_f4b6f33b-7991-4384-acfb-7cee8e727adb" xlink:to="loc_us-gaap_LongMember_8d09624f-24a0-4e0f-b012-058075fa720a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortMember_5eea3d72-ad80-4652-b7e3-8535356d7003" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShortMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PositionDomain_f4b6f33b-7991-4384-acfb-7cee8e727adb" xlink:to="loc_us-gaap_ShortMember_5eea3d72-ad80-4652-b7e3-8535356d7003" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.intlfcstone.com/role/RegulatoryCapitalRequirementsDetails" xlink:type="simple" xlink:href="intl-20230630.xsd#RegulatoryCapitalRequirementsDetails"/>
  <link:definitionLink xlink:role="http://www.intlfcstone.com/role/RegulatoryCapitalRequirementsDetails" xlink:type="extended" id="ib55181f5e6944ef1b1704cd18ef52c8c_RegulatoryCapitalRequirementsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_e7d5d7fb-1ff0-42b7-9f17-a66e1870529f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NetCapitalUnderCommodityExchangeActComputation_8317c623-a4ad-4dbf-a0b8-660bab734624" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_NetCapitalUnderCommodityExchangeActComputation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_e7d5d7fb-1ff0-42b7-9f17-a66e1870529f" xlink:to="loc_srt_NetCapitalUnderCommodityExchangeActComputation_8317c623-a4ad-4dbf-a0b8-660bab734624" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RequiredNetCapitalUnderCommodityExchangeAct1_4eddb014-e6fa-440f-839b-d76a5e4c2f0f" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RequiredNetCapitalUnderCommodityExchangeAct1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_e7d5d7fb-1ff0-42b7-9f17-a66e1870529f" xlink:to="loc_srt_RequiredNetCapitalUnderCommodityExchangeAct1_4eddb014-e6fa-440f-839b-d76a5e4c2f0f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsTable_4603d982-a206-4014-b817-9c7cb2ed12d4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_e7d5d7fb-1ff0-42b7-9f17-a66e1870529f" xlink:to="loc_us-gaap_ScheduleOfComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsTable_4603d982-a206-4014-b817-9c7cb2ed12d4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_a38a106e-ea2a-4060-b9f9-ba33d2a009a4" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsTable_4603d982-a206-4014-b817-9c7cb2ed12d4" xlink:to="loc_dei_LegalEntityAxis_a38a106e-ea2a-4060-b9f9-ba33d2a009a4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_a38a106e-ea2a-4060-b9f9-ba33d2a009a4_default" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_a38a106e-ea2a-4060-b9f9-ba33d2a009a4" xlink:to="loc_dei_EntityDomain_a38a106e-ea2a-4060-b9f9-ba33d2a009a4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_eba8d1b7-86b4-49ac-a244-a22755aeed76" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_a38a106e-ea2a-4060-b9f9-ba33d2a009a4" xlink:to="loc_dei_EntityDomain_eba8d1b7-86b4-49ac-a244-a22755aeed76" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_StoneXFinancialIncMember_e55c2cb4-94e2-4324-9c9e-1cd3861e9051" xlink:href="intl-20230630.xsd#intl_StoneXFinancialIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_eba8d1b7-86b4-49ac-a244-a22755aeed76" xlink:to="loc_intl_StoneXFinancialIncMember_e55c2cb4-94e2-4324-9c9e-1cd3861e9051" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_StoneXFinancialLtdMember_ea21576f-4874-4591-a6d8-1e35c9b95458" xlink:href="intl-20230630.xsd#intl_StoneXFinancialLtdMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_eba8d1b7-86b4-49ac-a244-a22755aeed76" xlink:to="loc_intl_StoneXFinancialLtdMember_ea21576f-4874-4591-a6d8-1e35c9b95458" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_GainCapitalGroupLLCMember_9c2ff785-dba8-4809-b2e6-40555971da0e" xlink:href="intl-20230630.xsd#intl_GainCapitalGroupLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_eba8d1b7-86b4-49ac-a244-a22755aeed76" xlink:to="loc_intl_GainCapitalGroupLLCMember_9c2ff785-dba8-4809-b2e6-40555971da0e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_StoneXFinancialPteLtdMember_4ca501ce-1528-432e-8bd4-2e0b22858953" xlink:href="intl-20230630.xsd#intl_StoneXFinancialPteLtdMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_eba8d1b7-86b4-49ac-a244-a22755aeed76" xlink:to="loc_intl_StoneXFinancialPteLtdMember_4ca501ce-1528-432e-8bd4-2e0b22858953" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_StoneXMarketsLLCMember_5bf3e750-5a28-4406-8704-ac140cec40a5" xlink:href="intl-20230630.xsd#intl_StoneXMarketsLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_eba8d1b7-86b4-49ac-a244-a22755aeed76" xlink:to="loc_intl_StoneXMarketsLLCMember_5bf3e750-5a28-4406-8704-ac140cec40a5" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.intlfcstone.com/role/AcquisitionsCottonDistributorsIncDetails" xlink:type="simple" xlink:href="intl-20230630.xsd#AcquisitionsCottonDistributorsIncDetails"/>
  <link:definitionLink xlink:role="http://www.intlfcstone.com/role/AcquisitionsCottonDistributorsIncDetails" xlink:type="extended" id="i11a28865f54340cab25398a6831d6913_AcquisitionsCottonDistributorsIncDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_fc4acbc8-0ae3-4014-bfa1-babe23d94c3a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_32804505-e708-4a41-8c3f-64aed79f777e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessCombinationConsiderationTransferred1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_fc4acbc8-0ae3-4014-bfa1-babe23d94c3a" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_32804505-e708-4a41-8c3f-64aed79f777e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesNetOfInterestExpense_88d6e8cd-00ea-4c68-a3bd-6f57f1044330" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenuesNetOfInterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_fc4acbc8-0ae3-4014-bfa1-babe23d94c3a" xlink:to="loc_us-gaap_RevenuesNetOfInterestExpense_88d6e8cd-00ea-4c68-a3bd-6f57f1044330" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_edf1fb32-620a-4b96-ba40-12082ec3094a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_fc4acbc8-0ae3-4014-bfa1-babe23d94c3a" xlink:to="loc_us-gaap_NetIncomeLoss_edf1fb32-620a-4b96-ba40-12082ec3094a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_a519b252-5265-4b08-8c71-b87147d3640c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_fc4acbc8-0ae3-4014-bfa1-babe23d94c3a" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_a519b252-5265-4b08-8c71-b87147d3640c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_5d205595-e131-4956-85a6-23a3dc9dad6f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_a519b252-5265-4b08-8c71-b87147d3640c" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_5d205595-e131-4956-85a6-23a3dc9dad6f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDepositsWithAndReceivablesFromBrokerDealersClearingOrganizationsAndCounterparties_345043ee-aa2c-4361-8969-7a9b1b2fbc69" xlink:href="intl-20230630.xsd#intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDepositsWithAndReceivablesFromBrokerDealersClearingOrganizationsAndCounterparties"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_a519b252-5265-4b08-8c71-b87147d3640c" xlink:to="loc_intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDepositsWithAndReceivablesFromBrokerDealersClearingOrganizationsAndCounterparties_345043ee-aa2c-4361-8969-7a9b1b2fbc69" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedReceivablesFromCustomers_290d78e7-739b-4462-b822-265a0fa72aa2" xlink:href="intl-20230630.xsd#intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedReceivablesFromCustomers"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_a519b252-5265-4b08-8c71-b87147d3640c" xlink:to="loc_intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedReceivablesFromCustomers_290d78e7-739b-4462-b822-265a0fa72aa2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedFinancialAssets_93d2d8e6-2a34-4b3b-bc5c-2b2a95c40e38" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedFinancialAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_a519b252-5265-4b08-8c71-b87147d3640c" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedFinancialAssets_93d2d8e6-2a34-4b3b-bc5c-2b2a95c40e38" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredIncomeTaxesNet_1b561910-a02c-4387-9d83-4fab02092cb7" xlink:href="intl-20230630.xsd#intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredIncomeTaxesNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_a519b252-5265-4b08-8c71-b87147d3640c" xlink:to="loc_intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredIncomeTaxesNet_1b561910-a02c-4387-9d83-4fab02092cb7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_88268f73-ca04-4488-a53b-ddeb324b99b0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_a519b252-5265-4b08-8c71-b87147d3640c" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_88268f73-ca04-4488-a53b-ddeb324b99b0" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory_432401a3-6b75-4c35-b656-b811bc02694e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_a519b252-5265-4b08-8c71-b87147d3640c" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory_432401a3-6b75-4c35-b656-b811bc02694e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherAssets_d92abeab-d8e5-413b-b27f-26ffe6d8448e" xlink:href="intl-20230630.xsd#intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_a519b252-5265-4b08-8c71-b87147d3640c" xlink:to="loc_intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherAssets_d92abeab-d8e5-413b-b27f-26ffe6d8448e" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedTangibleAssets_65fba020-0097-40f8-b41d-c981149ceb9f" xlink:href="intl-20230630.xsd#intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedTangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_a519b252-5265-4b08-8c71-b87147d3640c" xlink:to="loc_intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedTangibleAssets_65fba020-0097-40f8-b41d-c981149ceb9f" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccountsPayableAndOtherAccruedLiabilities_8e186742-a006-4285-8936-7c4f59d59c0e" xlink:href="intl-20230630.xsd#intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccountsPayableAndOtherAccruedLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_a519b252-5265-4b08-8c71-b87147d3640c" xlink:to="loc_intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccountsPayableAndOtherAccruedLiabilities_8e186742-a006-4285-8936-7c4f59d59c0e" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedFinancialInstrumentsSoldNotYetPurchasedAtFairValue_83c8547f-4d34-4661-ae07-2d977e9f2ca6" xlink:href="intl-20230630.xsd#intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedFinancialInstrumentsSoldNotYetPurchasedAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_a519b252-5265-4b08-8c71-b87147d3640c" xlink:to="loc_intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedFinancialInstrumentsSoldNotYetPurchasedAtFairValue_83c8547f-4d34-4661-ae07-2d977e9f2ca6" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPayableToLendersUnderLoans_7f66117b-bcea-4e0f-aeba-4eed0db38a68" xlink:href="intl-20230630.xsd#intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPayableToLendersUnderLoans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_a519b252-5265-4b08-8c71-b87147d3640c" xlink:to="loc_intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPayableToLendersUnderLoans_7f66117b-bcea-4e0f-aeba-4eed0db38a68" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedBrokerDealerPayableToOtherBrokerDealerAndClearingOrganization_b5f153e4-d5b8-4fe6-9e6a-46d2cb660e9a" xlink:href="intl-20230630.xsd#intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedBrokerDealerPayableToOtherBrokerDealerAndClearingOrganization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_a519b252-5265-4b08-8c71-b87147d3640c" xlink:to="loc_intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedBrokerDealerPayableToOtherBrokerDealerAndClearingOrganization_b5f153e4-d5b8-4fe6-9e6a-46d2cb660e9a" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedBrokerDealerPayableToCustomer_8d3128f2-6039-448e-888e-c2902a772283" xlink:href="intl-20230630.xsd#intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedBrokerDealerPayableToCustomer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_a519b252-5265-4b08-8c71-b87147d3640c" xlink:to="loc_intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedBrokerDealerPayableToCustomer_8d3128f2-6039-448e-888e-c2902a772283" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIncomeTaxesPayable_fb3387bc-a35e-4754-ba8e-c321ca6156b4" xlink:href="intl-20230630.xsd#intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIncomeTaxesPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_a519b252-5265-4b08-8c71-b87147d3640c" xlink:to="loc_intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIncomeTaxesPayable_fb3387bc-a35e-4754-ba8e-c321ca6156b4" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedTangibleLiabilities_8f8cbe92-7c73-4396-818e-8f599b21923d" xlink:href="intl-20230630.xsd#intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedTangibleLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_a519b252-5265-4b08-8c71-b87147d3640c" xlink:to="loc_intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedTangibleLiabilities_8f8cbe92-7c73-4396-818e-8f599b21923d" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAssetsAcquired_f98f0a32-41ff-4726-ae5c-111dcb8d4003" xlink:href="intl-20230630.xsd#intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAssetsAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_a519b252-5265-4b08-8c71-b87147d3640c" xlink:to="loc_intl_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAssetsAcquired_f98f0a32-41ff-4726-ae5c-111dcb8d4003" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_cca53765-785e-48be-90fd-611a1080f7b5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_a519b252-5265-4b08-8c71-b87147d3640c" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_cca53765-785e-48be-90fd-611a1080f7b5" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_6d2cb84d-429f-4ab4-a746-d16bb34e2b02" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_a519b252-5265-4b08-8c71-b87147d3640c" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_6d2cb84d-429f-4ab4-a746-d16bb34e2b02" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_7fbe07b4-2d07-4295-9c34-12c7d7878901" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessCombinationConsiderationTransferred1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationBargainPurchaseGainRecognizedAmount_d66b83da-d6cc-4b2a-ab0d-0dd03f8db09f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessCombinationBargainPurchaseGainRecognizedAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract_a519b252-5265-4b08-8c71-b87147d3640c" xlink:to="loc_us-gaap_BusinessCombinationBargainPurchaseGainRecognizedAmount_d66b83da-d6cc-4b2a-ab0d-0dd03f8db09f" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_029f032d-1150-4f78-a575-a698edab0621" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_fc4acbc8-0ae3-4014-bfa1-babe23d94c3a" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_029f032d-1150-4f78-a575-a698edab0621" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_41214b2c-32d3-4d91-9b0a-e1417f790cf4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_029f032d-1150-4f78-a575-a698edab0621" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_41214b2c-32d3-4d91-9b0a-e1417f790cf4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_41214b2c-32d3-4d91-9b0a-e1417f790cf4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_41214b2c-32d3-4d91-9b0a-e1417f790cf4" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_41214b2c-32d3-4d91-9b0a-e1417f790cf4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6864ba42-e500-480d-8e2d-f67b002b0415" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_41214b2c-32d3-4d91-9b0a-e1417f790cf4" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6864ba42-e500-480d-8e2d-f67b002b0415" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_CottonDistributorsIncMember_ce9c53f3-12f5-47fb-984d-b953e997baa5" xlink:href="intl-20230630.xsd#intl_CottonDistributorsIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6864ba42-e500-480d-8e2d-f67b002b0415" xlink:to="loc_intl_CottonDistributorsIncMember_ce9c53f3-12f5-47fb-984d-b953e997baa5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_329af81e-e067-45b4-b6c8-84e887119d1e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_029f032d-1150-4f78-a575-a698edab0621" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_329af81e-e067-45b4-b6c8-84e887119d1e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_329af81e-e067-45b4-b6c8-84e887119d1e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_329af81e-e067-45b4-b6c8-84e887119d1e" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_329af81e-e067-45b4-b6c8-84e887119d1e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_58ac2eb4-6840-4eb7-afd1-36dd31450693" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_329af81e-e067-45b4-b6c8-84e887119d1e" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_58ac2eb4-6840-4eb7-afd1-36dd31450693" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_462b934d-3a99-49ab-b899-6c0ea9c1304a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_58ac2eb4-6840-4eb7-afd1-36dd31450693" xlink:to="loc_us-gaap_CustomerRelationshipsMember_462b934d-3a99-49ab-b899-6c0ea9c1304a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_SupplierRelationshipMember_63d1c899-d1fa-42cf-995e-0cfb33f59b7c" xlink:href="intl-20230630.xsd#intl_SupplierRelationshipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_58ac2eb4-6840-4eb7-afd1-36dd31450693" xlink:to="loc_intl_SupplierRelationshipMember_63d1c899-d1fa-42cf-995e-0cfb33f59b7c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradeNamesMember_147de384-8e4d-49eb-9784-05ca121dbeb6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_58ac2eb4-6840-4eb7-afd1-36dd31450693" xlink:to="loc_us-gaap_TradeNamesMember_147de384-8e4d-49eb-9784-05ca121dbeb6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncompeteAgreementsMember_c8625422-f14f-4a13-a017-ef2c19bd2634" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NoncompeteAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_58ac2eb4-6840-4eb7-afd1-36dd31450693" xlink:to="loc_us-gaap_NoncompeteAgreementsMember_c8625422-f14f-4a13-a017-ef2c19bd2634" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.intlfcstone.com/role/AcquisitionsIncommSASDetails" xlink:type="simple" xlink:href="intl-20230630.xsd#AcquisitionsIncommSASDetails"/>
  <link:definitionLink xlink:role="http://www.intlfcstone.com/role/AcquisitionsIncommSASDetails" xlink:type="extended" id="ic5209cbc9cd74f1fb338657bf6633fec_AcquisitionsIncommSASDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_cd9f18f3-5025-46ce-8090-ec987104538d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_84c704b3-5cc1-49c9-ba5d-c5de75ff364f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessCombinationConsiderationTransferred1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_cd9f18f3-5025-46ce-8090-ec987104538d" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_84c704b3-5cc1-49c9-ba5d-c5de75ff364f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiability_97d1dc8a-dd09-4bbc-b4f4-11b6f5b318c9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessCombinationContingentConsiderationLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_cd9f18f3-5025-46ce-8090-ec987104538d" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiability_97d1dc8a-dd09-4bbc-b4f4-11b6f5b318c9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_BusinessCombinationContingentConsiderationLiabilityTerm_61a44207-0143-4564-9f22-300283a67af9" xlink:href="intl-20230630.xsd#intl_BusinessCombinationContingentConsiderationLiabilityTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_cd9f18f3-5025-46ce-8090-ec987104538d" xlink:to="loc_intl_BusinessCombinationContingentConsiderationLiabilityTerm_61a44207-0143-4564-9f22-300283a67af9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_143fd87a-fe89-4c49-9b0b-a222a385489e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_cd9f18f3-5025-46ce-8090-ec987104538d" xlink:to="loc_us-gaap_Goodwill_143fd87a-fe89-4c49-9b0b-a222a385489e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_609a0d32-2f28-427c-91d8-2e4cbfff2bb9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_cd9f18f3-5025-46ce-8090-ec987104538d" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_609a0d32-2f28-427c-91d8-2e4cbfff2bb9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_5ba9b174-082c-4773-a688-181b4270897a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_609a0d32-2f28-427c-91d8-2e4cbfff2bb9" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_5ba9b174-082c-4773-a688-181b4270897a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5ba9b174-082c-4773-a688-181b4270897a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_5ba9b174-082c-4773-a688-181b4270897a" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5ba9b174-082c-4773-a688-181b4270897a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_7029552d-6594-4cf3-9e59-cf4cb54e6b80" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_5ba9b174-082c-4773-a688-181b4270897a" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_7029552d-6594-4cf3-9e59-cf4cb54e6b80" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_IncommSASMember_d7035be9-d661-4829-b0e7-4314d43131d0" xlink:href="intl-20230630.xsd#intl_IncommSASMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_7029552d-6594-4cf3-9e59-cf4cb54e6b80" xlink:to="loc_intl_IncommSASMember_d7035be9-d661-4829-b0e7-4314d43131d0" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.intlfcstone.com/role/SegmentAnalysisNarrativeDetails" xlink:type="simple" xlink:href="intl-20230630.xsd#SegmentAnalysisNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.intlfcstone.com/role/SegmentAnalysisNarrativeDetails" xlink:type="extended" id="i076ed9ad4caa449b9a88af08a0de2972_SegmentAnalysisNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_7a203f11-4760-42d0-9ca5-1f4819228c28" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityNumberOfEmployees_2c939851-a476-483d-9e8a-281e27882f8a" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityNumberOfEmployees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_7a203f11-4760-42d0-9ca5-1f4819228c28" xlink:to="loc_dei_EntityNumberOfEmployees_2c939851-a476-483d-9e8a-281e27882f8a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfCountriesInWhichEntityOperates_722f92d8-d0ad-4bea-8980-69f4f160bc1f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NumberOfCountriesInWhichEntityOperates"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_7a203f11-4760-42d0-9ca5-1f4819228c28" xlink:to="loc_us-gaap_NumberOfCountriesInWhichEntityOperates_722f92d8-d0ad-4bea-8980-69f4f160bc1f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_NumberOfGlobalFinancialMarkets_e1bcbf52-8cba-4dbf-8e83-08461fe354e3" xlink:href="intl-20230630.xsd#intl_NumberOfGlobalFinancialMarkets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_7a203f11-4760-42d0-9ca5-1f4819228c28" xlink:to="loc_intl_NumberOfGlobalFinancialMarkets_e1bcbf52-8cba-4dbf-8e83-08461fe354e3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_NumberOfDifferentTypesOfForeignCurrencies_303e50a5-9405-4a30-9de1-02dcbf9ce6cd" xlink:href="intl-20230630.xsd#intl_NumberOfDifferentTypesOfForeignCurrencies"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_7a203f11-4760-42d0-9ca5-1f4819228c28" xlink:to="loc_intl_NumberOfDifferentTypesOfForeignCurrencies_303e50a5-9405-4a30-9de1-02dcbf9ce6cd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_0ba1fe0b-a65e-4867-ad4d-9e7c57595932" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_7a203f11-4760-42d0-9ca5-1f4819228c28" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_0ba1fe0b-a65e-4867-ad4d-9e7c57595932" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_0debd9c9-861a-4bda-8ee1-20319ea04ac8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_0ba1fe0b-a65e-4867-ad4d-9e7c57595932" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_0debd9c9-861a-4bda-8ee1-20319ea04ac8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_0debd9c9-861a-4bda-8ee1-20319ea04ac8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_0debd9c9-861a-4bda-8ee1-20319ea04ac8" xlink:to="loc_us-gaap_SegmentDomain_0debd9c9-861a-4bda-8ee1-20319ea04ac8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_877aabf8-da6b-48b4-82a1-01b9d380be3e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_0debd9c9-861a-4bda-8ee1-20319ea04ac8" xlink:to="loc_us-gaap_SegmentDomain_877aabf8-da6b-48b4-82a1-01b9d380be3e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_GlobalPaymentsSegmentMember_3a18df2e-e670-4931-a555-9d37b3b49d9c" xlink:href="intl-20230630.xsd#intl_GlobalPaymentsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_877aabf8-da6b-48b4-82a1-01b9d380be3e" xlink:to="loc_intl_GlobalPaymentsSegmentMember_3a18df2e-e670-4931-a555-9d37b3b49d9c" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.intlfcstone.com/role/SegmentAnalysisSegmentReportingDetails" xlink:type="simple" xlink:href="intl-20230630.xsd#SegmentAnalysisSegmentReportingDetails"/>
  <link:definitionLink xlink:role="http://www.intlfcstone.com/role/SegmentAnalysisSegmentReportingDetails" xlink:type="extended" id="i9e5464e6d02b4106bfd7fb8e96267a28_SegmentAnalysisSegmentReportingDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_867f14f4-ca05-4062-a9bb-4d6419c07863" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_f34a6c62-991c-4901-91f4-a3933438d0d9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_867f14f4-ca05-4062-a9bb-4d6419c07863" xlink:to="loc_us-gaap_Revenues_f34a6c62-991c-4901-91f4-a3933438d0d9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossProfit_18d386c1-0bb1-40cc-95a6-c56a93cd845f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GrossProfit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_867f14f4-ca05-4062-a9bb-4d6419c07863" xlink:to="loc_us-gaap_GrossProfit_18d386c1-0bb1-40cc-95a6-c56a93cd845f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesNetOfInterestExpense_f3a4a24b-6c9d-4ace-95b2-9a10865012ef" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenuesNetOfInterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_867f14f4-ca05-4062-a9bb-4d6419c07863" xlink:to="loc_us-gaap_RevenuesNetOfInterestExpense_f3a4a24b-6c9d-4ace-95b2-9a10865012ef" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_NetSegmentContribution_9c3a0af9-059a-4974-8485-be102a17a1f3" xlink:href="intl-20230630.xsd#intl_NetSegmentContribution"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_867f14f4-ca05-4062-a9bb-4d6419c07863" xlink:to="loc_intl_NetSegmentContribution_9c3a0af9-059a-4974-8485-be102a17a1f3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_SegmentIncome_536017c5-dfab-4850-adee-ca1ce280102f" xlink:href="intl-20230630.xsd#intl_SegmentIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_867f14f4-ca05-4062-a9bb-4d6419c07863" xlink:to="loc_intl_SegmentIncome_536017c5-dfab-4850-adee-ca1ce280102f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_UnallocatedCosts_3f8b6e48-13f9-413f-a019-11474bdbf886" xlink:href="intl-20230630.xsd#intl_UnallocatedCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_867f14f4-ca05-4062-a9bb-4d6419c07863" xlink:to="loc_intl_UnallocatedCosts_3f8b6e48-13f9-413f-a019-11474bdbf886" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingGainsLosses_2f4ecf88-fa1c-494f-90b0-aec0a876a2bc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherNonoperatingGainsLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_867f14f4-ca05-4062-a9bb-4d6419c07863" xlink:to="loc_us-gaap_OtherNonoperatingGainsLosses_2f4ecf88-fa1c-494f-90b0-aec0a876a2bc" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_1749d9c9-8f6d-41c2-b368-81403e415abb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_867f14f4-ca05-4062-a9bb-4d6419c07863" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_1749d9c9-8f6d-41c2-b368-81403e415abb" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_cdbadb5e-9029-4b29-b72a-7357b663c1b9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_867f14f4-ca05-4062-a9bb-4d6419c07863" xlink:to="loc_us-gaap_Assets_cdbadb5e-9029-4b29-b72a-7357b663c1b9" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_f2811dc3-56a2-4388-bd61-1da7cc9f0081" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_867f14f4-ca05-4062-a9bb-4d6419c07863" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_f2811dc3-56a2-4388-bd61-1da7cc9f0081" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_cdf8dc4e-278e-4b78-ab84-1595826b8093" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_f2811dc3-56a2-4388-bd61-1da7cc9f0081" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_cdf8dc4e-278e-4b78-ab84-1595826b8093" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_cdf8dc4e-278e-4b78-ab84-1595826b8093_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_cdf8dc4e-278e-4b78-ab84-1595826b8093" xlink:to="loc_us-gaap_SegmentDomain_cdf8dc4e-278e-4b78-ab84-1595826b8093_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_4126d035-24a4-4b08-9f32-a95ec1317544" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_cdf8dc4e-278e-4b78-ab84-1595826b8093" xlink:to="loc_us-gaap_SegmentDomain_4126d035-24a4-4b08-9f32-a95ec1317544" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_CommercialSegmentMember_aeef98ad-359e-4f1e-b1d1-a4c429fbb7d0" xlink:href="intl-20230630.xsd#intl_CommercialSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_4126d035-24a4-4b08-9f32-a95ec1317544" xlink:to="loc_intl_CommercialSegmentMember_aeef98ad-359e-4f1e-b1d1-a4c429fbb7d0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_InstitutionalSegmentMember_302a92a9-d59f-4687-90b2-89ec6cb6d4ba" xlink:href="intl-20230630.xsd#intl_InstitutionalSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_4126d035-24a4-4b08-9f32-a95ec1317544" xlink:to="loc_intl_InstitutionalSegmentMember_302a92a9-d59f-4687-90b2-89ec6cb6d4ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_RetailSegmentMember_f7aeb094-1bc5-4db2-b423-ab2862b0d2db" xlink:href="intl-20230630.xsd#intl_RetailSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_4126d035-24a4-4b08-9f32-a95ec1317544" xlink:to="loc_intl_RetailSegmentMember_f7aeb094-1bc5-4db2-b423-ab2862b0d2db" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_GlobalPaymentsSegmentMember_ca307025-e9a3-4e21-afcb-6c6c1bd56beb" xlink:href="intl-20230630.xsd#intl_GlobalPaymentsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_4126d035-24a4-4b08-9f32-a95ec1317544" xlink:to="loc_intl_GlobalPaymentsSegmentMember_ca307025-e9a3-4e21-afcb-6c6c1bd56beb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_3403d5ff-2e17-4446-9396-9295be15de13" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_f2811dc3-56a2-4388-bd61-1da7cc9f0081" xlink:to="loc_srt_ConsolidationItemsAxis_3403d5ff-2e17-4446-9396-9295be15de13" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_3403d5ff-2e17-4446-9396-9295be15de13_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_3403d5ff-2e17-4446-9396-9295be15de13" xlink:to="loc_srt_ConsolidationItemsDomain_3403d5ff-2e17-4446-9396-9295be15de13_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_1d583c6e-855c-4aba-bd91-da9fd93f4b5f" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_3403d5ff-2e17-4446-9396-9295be15de13" xlink:to="loc_srt_ConsolidationItemsDomain_1d583c6e-855c-4aba-bd91-da9fd93f4b5f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_6338ba61-58ef-40f8-8d50-3acf4631ba3e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_1d583c6e-855c-4aba-bd91-da9fd93f4b5f" xlink:to="loc_us-gaap_OperatingSegmentsMember_6338ba61-58ef-40f8-8d50-3acf4631ba3e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_1004976e-be76-40c4-a4f8-6bc075a4baa5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_1d583c6e-855c-4aba-bd91-da9fd93f4b5f" xlink:to="loc_us-gaap_CorporateNonSegmentMember_1004976e-be76-40c4-a4f8-6bc075a4baa5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntersegmentEliminationMember_8461dc2f-7b2d-4b45-b970-4d3a7d46b86f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IntersegmentEliminationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_1d583c6e-855c-4aba-bd91-da9fd93f4b5f" xlink:to="loc_us-gaap_IntersegmentEliminationMember_8461dc2f-7b2d-4b45-b970-4d3a7d46b86f" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/ecd/role/TradingArrangementsOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2023/ecd-2023.xsd#TradingArrangmentsOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/role/TradingArrangementsOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AllTradingArrangementsMember" xlink:href="https://xbrl.sec.gov/ecd/2023/ecd-2023.xsd#ecd_AllTradingArrangementsMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_DirectorTradingArrangementMember_b7d3130e-9ef1-4e1d-ab9f-895d015f29a5" xlink:href="intl-20230630.xsd#intl_DirectorTradingArrangementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllTradingArrangementsMember" xlink:to="loc_intl_DirectorTradingArrangementMember_b7d3130e-9ef1-4e1d-ab9f-895d015f29a5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_OfficeTradingArrangementMember_1de45b07-b790-4530-9389-5d2264e658e7" xlink:href="intl-20230630.xsd#intl_OfficeTradingArrangementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllTradingArrangementsMember" xlink:to="loc_intl_OfficeTradingArrangementMember_1de45b07-b790-4530-9389-5d2264e658e7" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2023/ecd-2023.xsd#IndividualsOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AllIndividualsMember" xlink:href="https://xbrl.sec.gov/ecd/2023/ecd-2023.xsd#ecd_AllIndividualsMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_intl_EricParthemoreMember_798a9cbf-8eea-4faa-8c47-7277742e0bbd" xlink:href="intl-20230630.xsd#intl_EricParthemoreMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_intl_EricParthemoreMember_798a9cbf-8eea-4faa-8c47-7277742e0bbd" xlink:type="arc" order="2"/>
  </link:definitionLink>
</link:linkbase>
