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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:d948df49-4073-47a9-bf4e-f8d545473eda,g:1e6644ec-a335-4cc3-af9f-418798d578de-->
<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.argenx.com/role/Unauditedcondensedconsolidatedinterimstatementsofchangesinequity" xlink:type="simple" xlink:href="argx-20260630.xsd#Unauditedcondensedconsolidatedinterimstatementsofchangesinequity"/>
  <link:definitionLink xlink:role="http://www.argenx.com/role/Unauditedcondensedconsolidatedinterimstatementsofchangesinequity" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_StatementOfChangesInEquityLineItems_c583959f-ee8a-4669-a7ec-feae944291f1" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_StatementOfChangesInEquityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_StatementOfChangesInEquityTable_c34445d8-ccdb-4a69-bd61-0713703ca722" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_StatementOfChangesInEquityTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_ifrs-full_StatementOfChangesInEquityLineItems_c583959f-ee8a-4669-a7ec-feae944291f1" xlink:to="loc_ifrs-full_StatementOfChangesInEquityTable_c34445d8-ccdb-4a69-bd61-0713703ca722" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_ComponentsOfEquityAxis_d6ad7fff-37ea-4fc6-9b0a-ae9f1e14db46" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_ComponentsOfEquityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ifrs-full_StatementOfChangesInEquityTable_c34445d8-ccdb-4a69-bd61-0713703ca722" xlink:to="loc_ifrs-full_ComponentsOfEquityAxis_d6ad7fff-37ea-4fc6-9b0a-ae9f1e14db46" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_ComponentsOfEquityDomain_d6ad7fff-37ea-4fc6-9b0a-ae9f1e14db46_default" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_ComponentsOfEquityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_ifrs-full_ComponentsOfEquityAxis_d6ad7fff-37ea-4fc6-9b0a-ae9f1e14db46" xlink:to="loc_ifrs-full_ComponentsOfEquityDomain_d6ad7fff-37ea-4fc6-9b0a-ae9f1e14db46_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_ComponentsOfEquityDomain_92b1857b-2ccb-4656-ae2a-0435b1a05da7" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_ComponentsOfEquityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_ifrs-full_ComponentsOfEquityAxis_d6ad7fff-37ea-4fc6-9b0a-ae9f1e14db46" xlink:to="loc_ifrs-full_ComponentsOfEquityDomain_92b1857b-2ccb-4656-ae2a-0435b1a05da7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_IssuedCapitalMember_056878bc-9d67-4eec-988a-a926170e42d3" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_IssuedCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_ComponentsOfEquityDomain_92b1857b-2ccb-4656-ae2a-0435b1a05da7" xlink:to="loc_ifrs-full_IssuedCapitalMember_056878bc-9d67-4eec-988a-a926170e42d3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_SharePremiumMember_265e8a40-95da-45d0-8439-f473fee48e5b" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_SharePremiumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_ComponentsOfEquityDomain_92b1857b-2ccb-4656-ae2a-0435b1a05da7" xlink:to="loc_ifrs-full_SharePremiumMember_265e8a40-95da-45d0-8439-f473fee48e5b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_RetainedEarningsMember_d5028453-7fc4-4a07-80bf-84af6f73902b" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_ComponentsOfEquityDomain_92b1857b-2ccb-4656-ae2a-0435b1a05da7" xlink:to="loc_ifrs-full_RetainedEarningsMember_d5028453-7fc4-4a07-80bf-84af6f73902b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_ReserveOfExchangeDifferencesOnTranslationMember_7bda001a-72d2-46c9-83bd-33dc8099e6aa" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_ReserveOfExchangeDifferencesOnTranslationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_ComponentsOfEquityDomain_92b1857b-2ccb-4656-ae2a-0435b1a05da7" xlink:to="loc_ifrs-full_ReserveOfExchangeDifferencesOnTranslationMember_7bda001a-72d2-46c9-83bd-33dc8099e6aa" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_ReserveOfSharebasedPaymentsMember_02bf2b04-3335-456b-90e3-491f24df33d0" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_ReserveOfSharebasedPaymentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_ComponentsOfEquityDomain_92b1857b-2ccb-4656-ae2a-0435b1a05da7" xlink:to="loc_ifrs-full_ReserveOfSharebasedPaymentsMember_02bf2b04-3335-456b-90e3-491f24df33d0" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_InvestmentsInEquityInstrumentsMeasuredAtFairValueThroughOtherComprehensiveIncomeMember_88734350-24f2-4eb9-9dab-22cb4b9976d9" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_InvestmentsInEquityInstrumentsMeasuredAtFairValueThroughOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_ComponentsOfEquityDomain_92b1857b-2ccb-4656-ae2a-0435b1a05da7" xlink:to="loc_ifrs-full_InvestmentsInEquityInstrumentsMeasuredAtFairValueThroughOtherComprehensiveIncomeMember_88734350-24f2-4eb9-9dab-22cb4b9976d9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_EquityAttributableToOwnersOfParentMember_94860422-683a-47f1-a550-29a7cc06c996" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_EquityAttributableToOwnersOfParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_ComponentsOfEquityDomain_92b1857b-2ccb-4656-ae2a-0435b1a05da7" xlink:to="loc_ifrs-full_EquityAttributableToOwnersOfParentMember_94860422-683a-47f1-a550-29a7cc06c996" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_Equity_8efa5885-95d4-4b41-889f-5a5531a95302" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_Equity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_StatementOfChangesInEquityLineItems_c583959f-ee8a-4669-a7ec-feae944291f1" xlink:to="loc_ifrs-full_Equity_8efa5885-95d4-4b41-889f-5a5531a95302" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_ProfitLoss_62b19a2c-7947-4527-944f-afdede135652" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_StatementOfChangesInEquityLineItems_c583959f-ee8a-4669-a7ec-feae944291f1" xlink:to="loc_ifrs-full_ProfitLoss_62b19a2c-7947-4527-944f-afdede135652" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_OtherComprehensiveIncome_f3292e55-1f86-4cf7-9ba2-102a113b2dd1" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_OtherComprehensiveIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_StatementOfChangesInEquityLineItems_c583959f-ee8a-4669-a7ec-feae944291f1" xlink:to="loc_ifrs-full_OtherComprehensiveIncome_f3292e55-1f86-4cf7-9ba2-102a113b2dd1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_ComprehensiveIncomeAttributableToOwnersOfParent_1398f03c-8178-461f-8538-2ae6c59777ea" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_ComprehensiveIncomeAttributableToOwnersOfParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_StatementOfChangesInEquityLineItems_c583959f-ee8a-4669-a7ec-feae944291f1" xlink:to="loc_ifrs-full_ComprehensiveIncomeAttributableToOwnersOfParent_1398f03c-8178-461f-8538-2ae6c59777ea" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_DecreaseIncreaseThroughTaxOnSharebasedPaymentTransactions_1991a37d-3fc4-45a4-9b59-508b77999025" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_DecreaseIncreaseThroughTaxOnSharebasedPaymentTransactions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_StatementOfChangesInEquityLineItems_c583959f-ee8a-4669-a7ec-feae944291f1" xlink:to="loc_ifrs-full_DecreaseIncreaseThroughTaxOnSharebasedPaymentTransactions_1991a37d-3fc4-45a4-9b59-508b77999025" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_IncreaseDecreaseThroughSharebasedPaymentTransactions_24d05c65-43b4-4b61-9b9b-e90da499242e" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_IncreaseDecreaseThroughSharebasedPaymentTransactions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_StatementOfChangesInEquityLineItems_c583959f-ee8a-4669-a7ec-feae944291f1" xlink:to="loc_ifrs-full_IncreaseDecreaseThroughSharebasedPaymentTransactions_24d05c65-43b4-4b61-9b9b-e90da499242e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_IncreaseDecreaseThroughExerciseOfOptionsEquity_c489d01e-d307-461f-9749-653fb9299d8b" xlink:href="argx-20260630.xsd#argx_IncreaseDecreaseThroughExerciseOfOptionsEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_StatementOfChangesInEquityLineItems_c583959f-ee8a-4669-a7ec-feae944291f1" xlink:to="loc_argx_IncreaseDecreaseThroughExerciseOfOptionsEquity_c489d01e-d307-461f-9749-653fb9299d8b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_DecreaseIncreaseThroughSharesWithheldForEmployeeTaxHoldingLiability_5aad8cc5-67e6-4179-8f3f-db63813f0a33" xlink:href="argx-20260630.xsd#argx_DecreaseIncreaseThroughSharesWithheldForEmployeeTaxHoldingLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_StatementOfChangesInEquityLineItems_c583959f-ee8a-4669-a7ec-feae944291f1" xlink:to="loc_argx_DecreaseIncreaseThroughSharesWithheldForEmployeeTaxHoldingLiability_5aad8cc5-67e6-4179-8f3f-db63813f0a33" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_Equity_ec0bddd0-d8ba-4b85-ae83-af6fa196978e" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_Equity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.argenx.com/role/TradeandotherreceivablesNarrativeDetails" xlink:type="simple" xlink:href="argx-20260630.xsd#TradeandotherreceivablesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.argenx.com/role/TradeandotherreceivablesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_DisclosureOfReconciliationOfChangesInLossAllowanceAndExplanationOfChangesInGrossCarryingAmountForFinancialInstrumentsLineItems_f09835d0-ecdd-48a5-82ab-0e180a8276a8" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_DisclosureOfReconciliationOfChangesInLossAllowanceAndExplanationOfChangesInGrossCarryingAmountForFinancialInstrumentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_DisclosureOfReconciliationOfChangesInLossAllowanceAndExplanationOfChangesInGrossCarryingAmountForFinancialInstrumentsTable_5ffd34d9-dcce-4bbf-8c7b-1d2dff2368d8" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_DisclosureOfReconciliationOfChangesInLossAllowanceAndExplanationOfChangesInGrossCarryingAmountForFinancialInstrumentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_ifrs-full_DisclosureOfReconciliationOfChangesInLossAllowanceAndExplanationOfChangesInGrossCarryingAmountForFinancialInstrumentsLineItems_f09835d0-ecdd-48a5-82ab-0e180a8276a8" xlink:to="loc_ifrs-full_DisclosureOfReconciliationOfChangesInLossAllowanceAndExplanationOfChangesInGrossCarryingAmountForFinancialInstrumentsTable_5ffd34d9-dcce-4bbf-8c7b-1d2dff2368d8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_CarryingAmountAccumulatedDepreciationAmortisationAndImpairmentAndGrossCarryingAmountAxis_71681150-baf7-4c56-9983-01dc773ebc5f" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_CarryingAmountAccumulatedDepreciationAmortisationAndImpairmentAndGrossCarryingAmountAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ifrs-full_DisclosureOfReconciliationOfChangesInLossAllowanceAndExplanationOfChangesInGrossCarryingAmountForFinancialInstrumentsTable_5ffd34d9-dcce-4bbf-8c7b-1d2dff2368d8" xlink:to="loc_ifrs-full_CarryingAmountAccumulatedDepreciationAmortisationAndImpairmentAndGrossCarryingAmountAxis_71681150-baf7-4c56-9983-01dc773ebc5f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_CarryingAmountMember_71681150-baf7-4c56-9983-01dc773ebc5f_default" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_CarryingAmountMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_ifrs-full_CarryingAmountAccumulatedDepreciationAmortisationAndImpairmentAndGrossCarryingAmountAxis_71681150-baf7-4c56-9983-01dc773ebc5f" xlink:to="loc_ifrs-full_CarryingAmountMember_71681150-baf7-4c56-9983-01dc773ebc5f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_CarryingAmountMember_e68c38f5-1f23-4269-88f1-850e0232be8e" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_CarryingAmountMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_ifrs-full_CarryingAmountAccumulatedDepreciationAmortisationAndImpairmentAndGrossCarryingAmountAxis_71681150-baf7-4c56-9983-01dc773ebc5f" xlink:to="loc_ifrs-full_CarryingAmountMember_e68c38f5-1f23-4269-88f1-850e0232be8e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_AccumulatedImpairmentMember_5416acdd-0c50-4dc6-a98a-20a55baf756d" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_AccumulatedImpairmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_CarryingAmountMember_e68c38f5-1f23-4269-88f1-850e0232be8e" xlink:to="loc_ifrs-full_AccumulatedImpairmentMember_5416acdd-0c50-4dc6-a98a-20a55baf756d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_ClassesOfFinancialInstrumentsAxis_4e01041d-ebf5-4c0b-803f-922729f32776" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_ClassesOfFinancialInstrumentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ifrs-full_DisclosureOfReconciliationOfChangesInLossAllowanceAndExplanationOfChangesInGrossCarryingAmountForFinancialInstrumentsTable_5ffd34d9-dcce-4bbf-8c7b-1d2dff2368d8" xlink:to="loc_ifrs-full_ClassesOfFinancialInstrumentsAxis_4e01041d-ebf5-4c0b-803f-922729f32776" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_ClassesOfFinancialInstrumentsDomain_4e01041d-ebf5-4c0b-803f-922729f32776_default" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_ClassesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_ifrs-full_ClassesOfFinancialInstrumentsAxis_4e01041d-ebf5-4c0b-803f-922729f32776" xlink:to="loc_ifrs-full_ClassesOfFinancialInstrumentsDomain_4e01041d-ebf5-4c0b-803f-922729f32776_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_ClassesOfFinancialInstrumentsDomain_a0c7396f-4c8b-454f-8c88-572a71e6e831" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_ClassesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_ifrs-full_ClassesOfFinancialInstrumentsAxis_4e01041d-ebf5-4c0b-803f-922729f32776" xlink:to="loc_ifrs-full_ClassesOfFinancialInstrumentsDomain_a0c7396f-4c8b-454f-8c88-572a71e6e831" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_TradeReceivablesMember_6186afbf-144d-403b-b236-7c98b1bb0416" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_TradeReceivablesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_ClassesOfFinancialInstrumentsDomain_a0c7396f-4c8b-454f-8c88-572a71e6e831" xlink:to="loc_ifrs-full_TradeReceivablesMember_6186afbf-144d-403b-b236-7c98b1bb0416" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_FinancialAssets_0abbbbaa-b835-4ea0-bf65-89cecca22d69" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_FinancialAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfReconciliationOfChangesInLossAllowanceAndExplanationOfChangesInGrossCarryingAmountForFinancialInstrumentsLineItems_f09835d0-ecdd-48a5-82ab-0e180a8276a8" xlink:to="loc_ifrs-full_FinancialAssets_0abbbbaa-b835-4ea0-bf65-89cecca22d69" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.argenx.com/role/FinancialassetsCurrentDetails" xlink:type="simple" xlink:href="argx-20260630.xsd#FinancialassetsCurrentDetails"/>
  <link:definitionLink xlink:role="http://www.argenx.com/role/FinancialassetsCurrentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_DisclosureOfFinancialAssetsLineItems_587a821e-bd53-44f9-8ba4-698f99033ba3" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_DisclosureOfFinancialAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_DisclosureOfFinancialAssetsTable_ce6b9c72-b255-4bd8-a112-0b3de5188690" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_DisclosureOfFinancialAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_ifrs-full_DisclosureOfFinancialAssetsLineItems_587a821e-bd53-44f9-8ba4-698f99033ba3" xlink:to="loc_ifrs-full_DisclosureOfFinancialAssetsTable_ce6b9c72-b255-4bd8-a112-0b3de5188690" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_ClassesOfFinancialAssetsAxis_00c833b1-ae08-4b8a-9d68-9d088a40bf33" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_ClassesOfFinancialAssetsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ifrs-full_DisclosureOfFinancialAssetsTable_ce6b9c72-b255-4bd8-a112-0b3de5188690" xlink:to="loc_ifrs-full_ClassesOfFinancialAssetsAxis_00c833b1-ae08-4b8a-9d68-9d088a40bf33" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_ClassesOfFinancialAssetsDomain_00c833b1-ae08-4b8a-9d68-9d088a40bf33_default" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_ClassesOfFinancialAssetsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_ifrs-full_ClassesOfFinancialAssetsAxis_00c833b1-ae08-4b8a-9d68-9d088a40bf33" xlink:to="loc_ifrs-full_ClassesOfFinancialAssetsDomain_00c833b1-ae08-4b8a-9d68-9d088a40bf33_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_ClassesOfFinancialAssetsDomain_8d72c8a5-379c-4a85-b5bb-b5fe1507efe4" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_ClassesOfFinancialAssetsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_ifrs-full_ClassesOfFinancialAssetsAxis_00c833b1-ae08-4b8a-9d68-9d088a40bf33" xlink:to="loc_ifrs-full_ClassesOfFinancialAssetsDomain_8d72c8a5-379c-4a85-b5bb-b5fe1507efe4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_TermAccountsMember_8e5da49f-36e2-4a3e-b6c8-8bb0224ef42c" xlink:href="argx-20260630.xsd#argx_TermAccountsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_ClassesOfFinancialAssetsDomain_8d72c8a5-379c-4a85-b5bb-b5fe1507efe4" xlink:to="loc_argx_TermAccountsMember_8e5da49f-36e2-4a3e-b6c8-8bb0224ef42c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_CurrentFinancialAssets_0ce969d6-0699-44ec-9d46-31cba90e6760" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_CurrentFinancialAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfFinancialAssetsLineItems_587a821e-bd53-44f9-8ba4-698f99033ba3" xlink:to="loc_ifrs-full_CurrentFinancialAssets_0ce969d6-0699-44ec-9d46-31cba90e6760" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.argenx.com/role/FinancialassetsCurrentNarrativeDetails" xlink:type="simple" xlink:href="argx-20260630.xsd#FinancialassetsCurrentNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.argenx.com/role/FinancialassetsCurrentNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_DisclosureOfFinancialAssetsLineItems_d22618fd-f8c9-43ff-9e09-a38ae8f3c347" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_DisclosureOfFinancialAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_DisclosureOfFinancialAssetsTable_b9cbd24b-eb6d-4309-99c1-51b67e9befe1" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_DisclosureOfFinancialAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_ifrs-full_DisclosureOfFinancialAssetsLineItems_d22618fd-f8c9-43ff-9e09-a38ae8f3c347" xlink:to="loc_ifrs-full_DisclosureOfFinancialAssetsTable_b9cbd24b-eb6d-4309-99c1-51b67e9befe1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CurrencyAxis_66e6f901-51f7-403f-991b-57e480d86f22" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_CurrencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ifrs-full_DisclosureOfFinancialAssetsTable_b9cbd24b-eb6d-4309-99c1-51b67e9befe1" xlink:to="loc_srt_CurrencyAxis_66e6f901-51f7-403f-991b-57e480d86f22" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_AllCurrenciesDomain_66e6f901-51f7-403f-991b-57e480d86f22_default" xlink:href="https://xbrl.sec.gov/currency/2025/currency-2025.xsd#currency_AllCurrenciesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CurrencyAxis_66e6f901-51f7-403f-991b-57e480d86f22" xlink:to="loc_currency_AllCurrenciesDomain_66e6f901-51f7-403f-991b-57e480d86f22_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_AllCurrenciesDomain_cca99f70-23de-4f14-bd31-7dd24754d25a" xlink:href="https://xbrl.sec.gov/currency/2025/currency-2025.xsd#currency_AllCurrenciesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CurrencyAxis_66e6f901-51f7-403f-991b-57e480d86f22" xlink:to="loc_currency_AllCurrenciesDomain_cca99f70-23de-4f14-bd31-7dd24754d25a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_ForeignCurrencyMember_019f652f-23f8-7528-adbc-b5ff9549c09a" xlink:href="argx-20260630.xsd#argx_ForeignCurrencyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_currency_AllCurrenciesDomain_cca99f70-23de-4f14-bd31-7dd24754d25a" xlink:to="loc_argx_ForeignCurrencyMember_019f652f-23f8-7528-adbc-b5ff9549c09a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_EUR_c26c8013-e387-471d-b3fa-82daee3cacba" xlink:href="https://xbrl.sec.gov/currency/2025/currency-2025.xsd#currency_EUR"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_currency_AllCurrenciesDomain_cca99f70-23de-4f14-bd31-7dd24754d25a" xlink:to="loc_currency_EUR_c26c8013-e387-471d-b3fa-82daee3cacba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_CurrentFinancialAssets_61c7c556-2c15-4d89-868c-f54e253325ec" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_CurrentFinancialAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfFinancialAssetsLineItems_d22618fd-f8c9-43ff-9e09-a38ae8f3c347" xlink:to="loc_ifrs-full_CurrentFinancialAssets_61c7c556-2c15-4d89-868c-f54e253325ec" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.argenx.com/role/CashandcashequivalentsNarrativeDetails" xlink:type="simple" xlink:href="argx-20260630.xsd#CashandcashequivalentsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.argenx.com/role/CashandcashequivalentsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_DisclosureOfFinancialAssetsLineItems_6d5f09b0-7c4d-497b-b52e-82705700a8e3" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_DisclosureOfFinancialAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_DisclosureOfFinancialAssetsTable_fb5c4d8a-76d8-47b2-bb67-d093a13b31c4" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_DisclosureOfFinancialAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_ifrs-full_DisclosureOfFinancialAssetsLineItems_6d5f09b0-7c4d-497b-b52e-82705700a8e3" xlink:to="loc_ifrs-full_DisclosureOfFinancialAssetsTable_fb5c4d8a-76d8-47b2-bb67-d093a13b31c4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CurrencyAxis_c72a935c-02ee-4873-a4f6-2d5d0292945c" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_CurrencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ifrs-full_DisclosureOfFinancialAssetsTable_fb5c4d8a-76d8-47b2-bb67-d093a13b31c4" xlink:to="loc_srt_CurrencyAxis_c72a935c-02ee-4873-a4f6-2d5d0292945c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_AllCurrenciesDomain_c72a935c-02ee-4873-a4f6-2d5d0292945c_default" xlink:href="https://xbrl.sec.gov/currency/2025/currency-2025.xsd#currency_AllCurrenciesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CurrencyAxis_c72a935c-02ee-4873-a4f6-2d5d0292945c" xlink:to="loc_currency_AllCurrenciesDomain_c72a935c-02ee-4873-a4f6-2d5d0292945c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_AllCurrenciesDomain_50f09741-04d9-4c93-bf66-bc32879ad4be" xlink:href="https://xbrl.sec.gov/currency/2025/currency-2025.xsd#currency_AllCurrenciesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CurrencyAxis_c72a935c-02ee-4873-a4f6-2d5d0292945c" xlink:to="loc_currency_AllCurrenciesDomain_50f09741-04d9-4c93-bf66-bc32879ad4be" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_EUR_b0d36471-92f5-4d25-96f5-2daddf03d57b" xlink:href="https://xbrl.sec.gov/currency/2025/currency-2025.xsd#currency_EUR"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_currency_AllCurrenciesDomain_50f09741-04d9-4c93-bf66-bc32879ad4be" xlink:to="loc_currency_EUR_b0d36471-92f5-4d25-96f5-2daddf03d57b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_CashAndCashEquivalents_d6fc21e7-436a-423a-a9d5-97368cafbb3a" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_CashAndCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfFinancialAssetsLineItems_6d5f09b0-7c4d-497b-b52e-82705700a8e3" xlink:to="loc_ifrs-full_CashAndCashEquivalents_d6fc21e7-436a-423a-a9d5-97368cafbb3a" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.argenx.com/role/SharebasedpaymentsStockoptionsNarrativeDetails" xlink:type="simple" xlink:href="argx-20260630.xsd#SharebasedpaymentsStockoptionsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.argenx.com/role/SharebasedpaymentsStockoptionsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems_93bb451b-8c41-4b63-85c7-3336bc2a976e" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable_b58f9304-4d33-4493-b5bb-d394ae1ab357" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems_93bb451b-8c41-4b63-85c7-3336bc2a976e" xlink:to="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable_b58f9304-4d33-4493-b5bb-d394ae1ab357" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_VestingRightAxis_ba61ff5e-b4aa-4896-8575-11fe1b4198e7" xlink:href="argx-20260630.xsd#argx_VestingRightAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable_b58f9304-4d33-4493-b5bb-d394ae1ab357" xlink:to="loc_argx_VestingRightAxis_ba61ff5e-b4aa-4896-8575-11fe1b4198e7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_VestingDomain_ba61ff5e-b4aa-4896-8575-11fe1b4198e7_default" xlink:href="argx-20260630.xsd#argx_VestingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_argx_VestingRightAxis_ba61ff5e-b4aa-4896-8575-11fe1b4198e7" xlink:to="loc_argx_VestingDomain_ba61ff5e-b4aa-4896-8575-11fe1b4198e7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_VestingDomain_bce81398-1443-4049-b138-966e4d7f5560" xlink:href="argx-20260630.xsd#argx_VestingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_argx_VestingRightAxis_ba61ff5e-b4aa-4896-8575-11fe1b4198e7" xlink:to="loc_argx_VestingDomain_bce81398-1443-4049-b138-966e4d7f5560" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_ShareBasedCompensationAwardTrancheOneMember_6406e833-c1e3-431a-8cee-de75301f0a0a" xlink:href="argx-20260630.xsd#argx_ShareBasedCompensationAwardTrancheOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_argx_VestingDomain_bce81398-1443-4049-b138-966e4d7f5560" xlink:to="loc_argx_ShareBasedCompensationAwardTrancheOneMember_6406e833-c1e3-431a-8cee-de75301f0a0a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_ShareBasedCompensationAwardTrancheTwoMember_0868ae8f-baa0-4be0-ac21-c80a0d9b2410" xlink:href="argx-20260630.xsd#argx_ShareBasedCompensationAwardTrancheTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_argx_VestingDomain_bce81398-1443-4049-b138-966e4d7f5560" xlink:to="loc_argx_ShareBasedCompensationAwardTrancheTwoMember_0868ae8f-baa0-4be0-ac21-c80a0d9b2410" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_CategoriesOfRelatedPartiesAxis_a72620e8-5d15-45ad-b1ff-0b18eac65de7" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_CategoriesOfRelatedPartiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable_b58f9304-4d33-4493-b5bb-d394ae1ab357" xlink:to="loc_ifrs-full_CategoriesOfRelatedPartiesAxis_a72620e8-5d15-45ad-b1ff-0b18eac65de7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_CategoriesOfRelatedPartiesDomain_a72620e8-5d15-45ad-b1ff-0b18eac65de7_default" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_CategoriesOfRelatedPartiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_ifrs-full_CategoriesOfRelatedPartiesAxis_a72620e8-5d15-45ad-b1ff-0b18eac65de7" xlink:to="loc_ifrs-full_CategoriesOfRelatedPartiesDomain_a72620e8-5d15-45ad-b1ff-0b18eac65de7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_CategoriesOfRelatedPartiesDomain_b81c0393-4868-41cd-9b11-8ef2de9c2982" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_CategoriesOfRelatedPartiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_ifrs-full_CategoriesOfRelatedPartiesAxis_a72620e8-5d15-45ad-b1ff-0b18eac65de7" xlink:to="loc_ifrs-full_CategoriesOfRelatedPartiesDomain_b81c0393-4868-41cd-9b11-8ef2de9c2982" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_NonExecutiveDirectorMember_ab87cfd2-ce44-467e-891f-8cf9d26cf578" xlink:href="argx-20260630.xsd#argx_NonExecutiveDirectorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_CategoriesOfRelatedPartiesDomain_b81c0393-4868-41cd-9b11-8ef2de9c2982" xlink:to="loc_argx_NonExecutiveDirectorMember_ab87cfd2-ce44-467e-891f-8cf9d26cf578" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_DirectorMember_019f477d-d5ba-772c-a600-710dac56d640" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_DirectorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_CategoriesOfRelatedPartiesDomain_b81c0393-4868-41cd-9b11-8ef2de9c2982" xlink:to="loc_srt_DirectorMember_019f477d-d5ba-772c-a600-710dac56d640" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsAxis_bab5f742-4fc6-4e43-9040-feccbfe69eea" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_TypesOfSharebasedPaymentArrangementsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable_b58f9304-4d33-4493-b5bb-d394ae1ab357" xlink:to="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsAxis_bab5f742-4fc6-4e43-9040-feccbfe69eea" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsDomain_bab5f742-4fc6-4e43-9040-feccbfe69eea_default" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_TypesOfSharebasedPaymentArrangementsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsAxis_bab5f742-4fc6-4e43-9040-feccbfe69eea" xlink:to="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsDomain_bab5f742-4fc6-4e43-9040-feccbfe69eea_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsDomain_38318840-8ebf-4306-84ae-275b2f53fc61" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_TypesOfSharebasedPaymentArrangementsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsAxis_bab5f742-4fc6-4e43-9040-feccbfe69eea" xlink:to="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsDomain_38318840-8ebf-4306-84ae-275b2f53fc61" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_StockOptionPlanMember_4630f79b-788e-4151-84e6-207ddc1c63dc" xlink:href="argx-20260630.xsd#argx_StockOptionPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsDomain_38318840-8ebf-4306-84ae-275b2f53fc61" xlink:to="loc_argx_StockOptionPlanMember_4630f79b-788e-4151-84e6-207ddc1c63dc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_GrantAwardDateAxis_019f477e-b7ba-7422-8d5f-2a1772af2e14" xlink:href="argx-20260630.xsd#argx_GrantAwardDateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable_b58f9304-4d33-4493-b5bb-d394ae1ab357" xlink:to="loc_argx_GrantAwardDateAxis_019f477e-b7ba-7422-8d5f-2a1772af2e14" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_GrantAwardDateDomain_019f477e-b7ba-7422-8d5f-2a1772af2e14_default" xlink:href="argx-20260630.xsd#argx_GrantAwardDateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_argx_GrantAwardDateAxis_019f477e-b7ba-7422-8d5f-2a1772af2e14" xlink:to="loc_argx_GrantAwardDateDomain_019f477e-b7ba-7422-8d5f-2a1772af2e14_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_GrantAwardDateDomain_019f477e-b7ba-7194-8b44-247826bdd1c5" xlink:href="argx-20260630.xsd#argx_GrantAwardDateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_argx_GrantAwardDateAxis_019f477e-b7ba-7422-8d5f-2a1772af2e14" xlink:to="loc_argx_GrantAwardDateDomain_019f477e-b7ba-7194-8b44-247826bdd1c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_January12026GrantsMember_019f477e-b7ba-7a3b-bddd-852c3a50e485" xlink:href="argx-20260630.xsd#argx_January12026GrantsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_argx_GrantAwardDateDomain_019f477e-b7ba-7194-8b44-247826bdd1c5" xlink:to="loc_argx_January12026GrantsMember_019f477e-b7ba-7a3b-bddd-852c3a50e485" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_ConversionOfStockSharesIssued_bb02b149-6b0b-4f8a-a9bc-a3502085c8c3" xlink:href="argx-20260630.xsd#argx_ConversionOfStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems_93bb451b-8c41-4b63-85c7-3336bc2a976e" xlink:to="loc_argx_ConversionOfStockSharesIssued_bb02b149-6b0b-4f8a-a9bc-a3502085c8c3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRightsPercentage_d86f2097-ac71-49ba-b6db-a886a8181377" xlink:href="argx-20260630.xsd#argx_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRightsPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems_93bb451b-8c41-4b63-85c7-3336bc2a976e" xlink:to="loc_argx_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRightsPercentage_d86f2097-ac71-49ba-b6db-a886a8181377" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_VestingRequirementsForShareBasedPaymentArrangementVestingPeriod_08099e21-727a-4c93-9181-8d7481dda933" xlink:href="argx-20260630.xsd#argx_VestingRequirementsForShareBasedPaymentArrangementVestingPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems_93bb451b-8c41-4b63-85c7-3336bc2a976e" xlink:to="loc_argx_VestingRequirementsForShareBasedPaymentArrangementVestingPeriod_08099e21-727a-4c93-9181-8d7481dda933" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_ExpenseFromSharebasedPaymentTransactionsWithEmployees_c3fd758e-10c2-4a9f-bb18-4c584b6f2342" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_ExpenseFromSharebasedPaymentTransactionsWithEmployees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems_93bb451b-8c41-4b63-85c7-3336bc2a976e" xlink:to="loc_ifrs-full_ExpenseFromSharebasedPaymentTransactionsWithEmployees_c3fd758e-10c2-4a9f-bb18-4c584b6f2342" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.argenx.com/role/SharebasedpaymentsScheduleofparametersusedinrelationtothenewgrantsDetails" xlink:type="simple" xlink:href="argx-20260630.xsd#SharebasedpaymentsScheduleofparametersusedinrelationtothenewgrantsDetails"/>
  <link:definitionLink xlink:role="http://www.argenx.com/role/SharebasedpaymentsScheduleofparametersusedinrelationtothenewgrantsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems_e2d1b772-dc23-48e5-8781-404c28fb132a" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable_949b5d6e-0892-43ff-81d7-aad15d08e15e" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems_e2d1b772-dc23-48e5-8781-404c28fb132a" xlink:to="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable_949b5d6e-0892-43ff-81d7-aad15d08e15e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_RangeAxis_814a1c78-71ed-46ce-bf7a-8b42a0f8bdbf" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable_949b5d6e-0892-43ff-81d7-aad15d08e15e" xlink:to="loc_ifrs-full_RangeAxis_814a1c78-71ed-46ce-bf7a-8b42a0f8bdbf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_RangeDomain_814a1c78-71ed-46ce-bf7a-8b42a0f8bdbf_default" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_RangeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_ifrs-full_RangeAxis_814a1c78-71ed-46ce-bf7a-8b42a0f8bdbf" xlink:to="loc_ifrs-full_RangeDomain_814a1c78-71ed-46ce-bf7a-8b42a0f8bdbf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_RangeDomain_e7dd94bd-71a0-4446-bbba-7cd769975f2e" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_RangeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_ifrs-full_RangeAxis_814a1c78-71ed-46ce-bf7a-8b42a0f8bdbf" xlink:to="loc_ifrs-full_RangeDomain_e7dd94bd-71a0-4446-bbba-7cd769975f2e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_BottomOfRangeMember_8a00eae7-0916-405e-a3b7-7ad15eb0c2ee" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_BottomOfRangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_RangeDomain_e7dd94bd-71a0-4446-bbba-7cd769975f2e" xlink:to="loc_ifrs-full_BottomOfRangeMember_8a00eae7-0916-405e-a3b7-7ad15eb0c2ee" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_TopOfRangeMember_5d9ad3b8-75d5-4d2f-b4a3-03b771954b98" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_TopOfRangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_RangeDomain_e7dd94bd-71a0-4446-bbba-7cd769975f2e" xlink:to="loc_ifrs-full_TopOfRangeMember_5d9ad3b8-75d5-4d2f-b4a3-03b771954b98" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_GranteeAwardStatusAxis_4c72f533-08e0-4f20-81da-089bd3fcb661" xlink:href="argx-20260630.xsd#argx_GranteeAwardStatusAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable_949b5d6e-0892-43ff-81d7-aad15d08e15e" xlink:to="loc_argx_GranteeAwardStatusAxis_4c72f533-08e0-4f20-81da-089bd3fcb661" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_GranteeAwardStatusDomain_4c72f533-08e0-4f20-81da-089bd3fcb661_default" xlink:href="argx-20260630.xsd#argx_GranteeAwardStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_argx_GranteeAwardStatusAxis_4c72f533-08e0-4f20-81da-089bd3fcb661" xlink:to="loc_argx_GranteeAwardStatusDomain_4c72f533-08e0-4f20-81da-089bd3fcb661_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_GranteeAwardStatusDomain_7541d680-875f-48cb-9c0e-0369886cd6a1" xlink:href="argx-20260630.xsd#argx_GranteeAwardStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_argx_GranteeAwardStatusAxis_4c72f533-08e0-4f20-81da-089bd3fcb661" xlink:to="loc_argx_GranteeAwardStatusDomain_7541d680-875f-48cb-9c0e-0369886cd6a1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_BelgianTaxedBeneficiariesMember_7bbede69-f9dd-4b56-b56c-6b5ca2b015af" xlink:href="argx-20260630.xsd#argx_BelgianTaxedBeneficiariesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_argx_GranteeAwardStatusDomain_7541d680-875f-48cb-9c0e-0369886cd6a1" xlink:to="loc_argx_BelgianTaxedBeneficiariesMember_7bbede69-f9dd-4b56-b56c-6b5ca2b015af" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_NumberOfShareOptionsGrantedInSharebasedPaymentArrangement_f2ad92c6-0cb2-440a-82da-d2ab9fe48beb" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_NumberOfShareOptionsGrantedInSharebasedPaymentArrangement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems_e2d1b772-dc23-48e5-8781-404c28fb132a" xlink:to="loc_ifrs-full_NumberOfShareOptionsGrantedInSharebasedPaymentArrangement_f2ad92c6-0cb2-440a-82da-d2ab9fe48beb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_WeightedAverageFairValueAtMeasurementDatePerShareOptionsGranted_cf7f4215-d3f9-4663-a1ef-1f703c15fac9" xlink:href="argx-20260630.xsd#argx_WeightedAverageFairValueAtMeasurementDatePerShareOptionsGranted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems_e2d1b772-dc23-48e5-8781-404c28fb132a" xlink:to="loc_argx_WeightedAverageFairValueAtMeasurementDatePerShareOptionsGranted_cf7f4215-d3f9-4663-a1ef-1f703c15fac9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_WeightedAverageSharePriceShareOptionsGranted2019_1593bc7e-dd95-410b-b4e8-1610c2a1f74e" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_WeightedAverageSharePriceShareOptionsGranted2019"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems_e2d1b772-dc23-48e5-8781-404c28fb132a" xlink:to="loc_ifrs-full_WeightedAverageSharePriceShareOptionsGranted2019_1593bc7e-dd95-410b-b4e8-1610c2a1f74e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_ExercisePriceOfOutstandingShareOptions2019_0ff08100-d2e7-4152-8990-3b3c4537de11" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_ExercisePriceOfOutstandingShareOptions2019"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems_e2d1b772-dc23-48e5-8781-404c28fb132a" xlink:to="loc_ifrs-full_ExercisePriceOfOutstandingShareOptions2019_0ff08100-d2e7-4152-8990-3b3c4537de11" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_DescriptionOfExpectedVolatilityShareOptionsGranted_b946c126-98e6-4f48-a10a-e44659a3e5e1" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_DescriptionOfExpectedVolatilityShareOptionsGranted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems_e2d1b772-dc23-48e5-8781-404c28fb132a" xlink:to="loc_ifrs-full_DescriptionOfExpectedVolatilityShareOptionsGranted_b946c126-98e6-4f48-a10a-e44659a3e5e1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_DescriptionOfOptionLifeShareOptionsGranted_2be32d2c-d13e-4513-acc1-2c07a5e923a2" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_DescriptionOfOptionLifeShareOptionsGranted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems_e2d1b772-dc23-48e5-8781-404c28fb132a" xlink:to="loc_ifrs-full_DescriptionOfOptionLifeShareOptionsGranted_2be32d2c-d13e-4513-acc1-2c07a5e923a2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_DescriptionOfRiskFreeInterestRateShareOptionsGranted_7f06de6a-edbe-4b62-90b1-5ee6a8d77ed7" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_DescriptionOfRiskFreeInterestRateShareOptionsGranted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems_e2d1b772-dc23-48e5-8781-404c28fb132a" xlink:to="loc_ifrs-full_DescriptionOfRiskFreeInterestRateShareOptionsGranted_7f06de6a-edbe-4b62-90b1-5ee6a8d77ed7" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_ExpectedDividendAsPercentageShareOptionsGranted_c8f039e2-2dd2-4251-892d-8fcc8d36160d" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_ExpectedDividendAsPercentageShareOptionsGranted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems_e2d1b772-dc23-48e5-8781-404c28fb132a" xlink:to="loc_ifrs-full_ExpectedDividendAsPercentageShareOptionsGranted_c8f039e2-2dd2-4251-892d-8fcc8d36160d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_PercentageOfShareOptionsGrantedOfTotalShareOptions_019f642d-9c6a-799f-94e1-b9e5a517c5d3" xlink:href="argx-20260630.xsd#argx_PercentageOfShareOptionsGrantedOfTotalShareOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems_e2d1b772-dc23-48e5-8781-404c28fb132a" xlink:to="loc_argx_PercentageOfShareOptionsGrantedOfTotalShareOptions_019f642d-9c6a-799f-94e1-b9e5a517c5d3" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_TimePeriodToChooseDifferentContractualTerms_52cda753-94ac-4584-baf2-8dc519e24b7c" xlink:href="argx-20260630.xsd#argx_TimePeriodToChooseDifferentContractualTerms"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems_e2d1b772-dc23-48e5-8781-404c28fb132a" xlink:to="loc_argx_TimePeriodToChooseDifferentContractualTerms_52cda753-94ac-4584-baf2-8dc519e24b7c" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.argenx.com/role/SharebasedpaymentsRestrictedStockUnitsRSUsDetails" xlink:type="simple" xlink:href="argx-20260630.xsd#SharebasedpaymentsRestrictedStockUnitsRSUsDetails"/>
  <link:definitionLink xlink:role="http://www.argenx.com/role/SharebasedpaymentsRestrictedStockUnitsRSUsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems_db59c587-1498-436d-9df4-05813fa3ec76" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable_0b7d1e21-24cf-4271-893a-f4412ee9d6a6" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems_db59c587-1498-436d-9df4-05813fa3ec76" xlink:to="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable_0b7d1e21-24cf-4271-893a-f4412ee9d6a6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsAxis_2e907d2b-0a24-49c7-9d15-dcbf0e580911" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_TypesOfSharebasedPaymentArrangementsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable_0b7d1e21-24cf-4271-893a-f4412ee9d6a6" xlink:to="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsAxis_2e907d2b-0a24-49c7-9d15-dcbf0e580911" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsDomain_2e907d2b-0a24-49c7-9d15-dcbf0e580911_default" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_TypesOfSharebasedPaymentArrangementsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsAxis_2e907d2b-0a24-49c7-9d15-dcbf0e580911" xlink:to="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsDomain_2e907d2b-0a24-49c7-9d15-dcbf0e580911_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsDomain_0f587e9f-c988-42b8-87b0-0316f98705ac" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_TypesOfSharebasedPaymentArrangementsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsAxis_2e907d2b-0a24-49c7-9d15-dcbf0e580911" xlink:to="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsDomain_0f587e9f-c988-42b8-87b0-0316f98705ac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_IfrsRestrictedStockUnitsRsusMember_8a846485-885c-4566-8030-1eb7d12ba52e" xlink:href="argx-20260630.xsd#argx_IfrsRestrictedStockUnitsRsusMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsDomain_0f587e9f-c988-42b8-87b0-0316f98705ac" xlink:to="loc_argx_IfrsRestrictedStockUnitsRsusMember_8a846485-885c-4566-8030-1eb7d12ba52e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_CategoriesOfRelatedPartiesAxis_301d59ee-867d-4b91-8bc6-66a7ccb2f5c2" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_CategoriesOfRelatedPartiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable_0b7d1e21-24cf-4271-893a-f4412ee9d6a6" xlink:to="loc_ifrs-full_CategoriesOfRelatedPartiesAxis_301d59ee-867d-4b91-8bc6-66a7ccb2f5c2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_CategoriesOfRelatedPartiesDomain_301d59ee-867d-4b91-8bc6-66a7ccb2f5c2_default" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_CategoriesOfRelatedPartiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_ifrs-full_CategoriesOfRelatedPartiesAxis_301d59ee-867d-4b91-8bc6-66a7ccb2f5c2" xlink:to="loc_ifrs-full_CategoriesOfRelatedPartiesDomain_301d59ee-867d-4b91-8bc6-66a7ccb2f5c2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_CategoriesOfRelatedPartiesDomain_dbd08512-4497-4a85-9b95-a97e728e1c44" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_CategoriesOfRelatedPartiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_ifrs-full_CategoriesOfRelatedPartiesAxis_301d59ee-867d-4b91-8bc6-66a7ccb2f5c2" xlink:to="loc_ifrs-full_CategoriesOfRelatedPartiesDomain_dbd08512-4497-4a85-9b95-a97e728e1c44" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_NonExecutiveDirectorMember_72282c0e-7364-4693-9653-33d53bd1c533" xlink:href="argx-20260630.xsd#argx_NonExecutiveDirectorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_CategoriesOfRelatedPartiesDomain_dbd08512-4497-4a85-9b95-a97e728e1c44" xlink:to="loc_argx_NonExecutiveDirectorMember_72282c0e-7364-4693-9653-33d53bd1c533" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_GrantAwardDateAxis_019f470a-a4cc-73ae-a914-e74869320f5e" xlink:href="argx-20260630.xsd#argx_GrantAwardDateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable_0b7d1e21-24cf-4271-893a-f4412ee9d6a6" xlink:to="loc_argx_GrantAwardDateAxis_019f470a-a4cc-73ae-a914-e74869320f5e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_GrantAwardDateDomain_019f470a-a4cc-73ae-a914-e74869320f5e_default" xlink:href="argx-20260630.xsd#argx_GrantAwardDateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_argx_GrantAwardDateAxis_019f470a-a4cc-73ae-a914-e74869320f5e" xlink:to="loc_argx_GrantAwardDateDomain_019f470a-a4cc-73ae-a914-e74869320f5e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_GrantAwardDateDomain_019f470a-a4cc-71ee-8e47-da7fc994b976" xlink:href="argx-20260630.xsd#argx_GrantAwardDateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_argx_GrantAwardDateAxis_019f470a-a4cc-73ae-a914-e74869320f5e" xlink:to="loc_argx_GrantAwardDateDomain_019f470a-a4cc-71ee-8e47-da7fc994b976" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_PriorTo2024GrantsMember_019f470b-db73-727f-b4b8-478fd45ae45a" xlink:href="argx-20260630.xsd#argx_PriorTo2024GrantsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_argx_GrantAwardDateDomain_019f470a-a4cc-71ee-8e47-da7fc994b976" xlink:to="loc_argx_PriorTo2024GrantsMember_019f470b-db73-727f-b4b8-478fd45ae45a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_A20242025GrantsMember_019f470c-5395-7fd5-aaa8-f38e33a49849" xlink:href="argx-20260630.xsd#argx_A20242025GrantsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_argx_GrantAwardDateDomain_019f470a-a4cc-71ee-8e47-da7fc994b976" xlink:to="loc_argx_A20242025GrantsMember_019f470c-5395-7fd5-aaa8-f38e33a49849" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_January12026GrantsMember_019f470c-8dc8-7a0b-b065-27d7ca5b31de" xlink:href="argx-20260630.xsd#argx_January12026GrantsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_argx_GrantAwardDateDomain_019f470a-a4cc-71ee-8e47-da7fc994b976" xlink:to="loc_argx_January12026GrantsMember_019f470c-8dc8-7a0b-b065-27d7ca5b31de" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_ConversionOfStockSharesIssued_d4179f45-dbf6-4024-aba9-4d7176bf86b6" xlink:href="argx-20260630.xsd#argx_ConversionOfStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems_db59c587-1498-436d-9df4-05813fa3ec76" xlink:to="loc_argx_ConversionOfStockSharesIssued_d4179f45-dbf6-4024-aba9-4d7176bf86b6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod_854ef104-f7ac-4261-b873-ac672fbad306" xlink:href="argx-20260630.xsd#argx_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems_db59c587-1498-436d-9df4-05813fa3ec76" xlink:to="loc_argx_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod_854ef104-f7ac-4261-b873-ac672fbad306" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_VestingRequirementsForShareBasedPaymentArrangementHoldingPeriod_d33766ad-33e9-4601-9e51-9d73e3a72f58" xlink:href="argx-20260630.xsd#argx_VestingRequirementsForShareBasedPaymentArrangementHoldingPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems_db59c587-1498-436d-9df4-05813fa3ec76" xlink:to="loc_argx_VestingRequirementsForShareBasedPaymentArrangementHoldingPeriod_d33766ad-33e9-4601-9e51-9d73e3a72f58" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRightsPercentage_3bdf5ddf-59af-4ae3-b592-915fe1ab16ae" xlink:href="argx-20260630.xsd#argx_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRightsPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems_db59c587-1498-436d-9df4-05813fa3ec76" xlink:to="loc_argx_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRightsPercentage_3bdf5ddf-59af-4ae3-b592-915fe1ab16ae" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_ExpenseFromSharebasedPaymentTransactionsWithEmployees_6806e7a9-54cd-41ad-821b-2b1c3b4a0a06" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_ExpenseFromSharebasedPaymentTransactionsWithEmployees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems_db59c587-1498-436d-9df4-05813fa3ec76" xlink:to="loc_ifrs-full_ExpenseFromSharebasedPaymentTransactionsWithEmployees_6806e7a9-54cd-41ad-821b-2b1c3b4a0a06" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_VestingRequirementsForShareBasedPaymentArrangementVestingPeriod_6f62c0e9-534f-462a-bce2-32936016b42f" xlink:href="argx-20260630.xsd#argx_VestingRequirementsForShareBasedPaymentArrangementVestingPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems_db59c587-1498-436d-9df4-05813fa3ec76" xlink:to="loc_argx_VestingRequirementsForShareBasedPaymentArrangementVestingPeriod_6f62c0e9-534f-462a-bce2-32936016b42f" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.argenx.com/role/SharebasedpaymentsPerformanceStockUnitsPSUsDetails" xlink:type="simple" xlink:href="argx-20260630.xsd#SharebasedpaymentsPerformanceStockUnitsPSUsDetails"/>
  <link:definitionLink xlink:role="http://www.argenx.com/role/SharebasedpaymentsPerformanceStockUnitsPSUsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems_688bdda3-3ebe-4ba5-a586-33de3985fdb2" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable_52d4b0ef-ce83-4b9a-805d-c3de1f835161" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems_688bdda3-3ebe-4ba5-a586-33de3985fdb2" xlink:to="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable_52d4b0ef-ce83-4b9a-805d-c3de1f835161" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsAxis_175fdf8e-5b56-425d-8c60-f816bb28b56c" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_TypesOfSharebasedPaymentArrangementsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementTable_52d4b0ef-ce83-4b9a-805d-c3de1f835161" xlink:to="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsAxis_175fdf8e-5b56-425d-8c60-f816bb28b56c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsDomain_175fdf8e-5b56-425d-8c60-f816bb28b56c_default" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_TypesOfSharebasedPaymentArrangementsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsAxis_175fdf8e-5b56-425d-8c60-f816bb28b56c" xlink:to="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsDomain_175fdf8e-5b56-425d-8c60-f816bb28b56c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsDomain_786e4911-a57f-4d24-b5dd-10cfded5e889" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_TypesOfSharebasedPaymentArrangementsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsAxis_175fdf8e-5b56-425d-8c60-f816bb28b56c" xlink:to="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsDomain_786e4911-a57f-4d24-b5dd-10cfded5e889" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_PerformanceStockUnitsPSUsMember_628e9d02-55dc-4938-a9f7-332566671695" xlink:href="argx-20260630.xsd#argx_PerformanceStockUnitsPSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsDomain_786e4911-a57f-4d24-b5dd-10cfded5e889" xlink:to="loc_argx_PerformanceStockUnitsPSUsMember_628e9d02-55dc-4938-a9f7-332566671695" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_ConversionOfStockSharesIssued_a88205be-ff1a-413a-981e-a1731f580cc2" xlink:href="argx-20260630.xsd#argx_ConversionOfStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems_688bdda3-3ebe-4ba5-a586-33de3985fdb2" xlink:to="loc_argx_ConversionOfStockSharesIssued_a88205be-ff1a-413a-981e-a1731f580cc2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_VestingRequirementsForShareBasedPaymentArrangementVestingPeriod_88afcbc4-aafa-48da-87bf-2a610eae850e" xlink:href="argx-20260630.xsd#argx_VestingRequirementsForShareBasedPaymentArrangementVestingPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems_688bdda3-3ebe-4ba5-a586-33de3985fdb2" xlink:to="loc_argx_VestingRequirementsForShareBasedPaymentArrangementVestingPeriod_88afcbc4-aafa-48da-87bf-2a610eae850e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_ShareBasedPaymentAgreementMaximumUpsidePayoutPercentage_fa4ff9da-399a-45d7-8024-19145f22b1be" xlink:href="argx-20260630.xsd#argx_ShareBasedPaymentAgreementMaximumUpsidePayoutPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems_688bdda3-3ebe-4ba5-a586-33de3985fdb2" xlink:to="loc_argx_ShareBasedPaymentAgreementMaximumUpsidePayoutPercentage_fa4ff9da-399a-45d7-8024-19145f22b1be" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_ExpenseFromSharebasedPaymentTransactionsWithEmployees_019f4781-85b0-78f0-8950-5ee3099628d5" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_ExpenseFromSharebasedPaymentTransactionsWithEmployees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfTermsAndConditionsOfSharebasedPaymentArrangementLineItems_688bdda3-3ebe-4ba5-a586-33de3985fdb2" xlink:to="loc_ifrs-full_ExpenseFromSharebasedPaymentTransactionsWithEmployees_019f4781-85b0-78f0-8950-5ee3099628d5" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.argenx.com/role/TradeandotherpayablesMovementinthesalesrebatesandreservesDetails" xlink:type="simple" xlink:href="argx-20260630.xsd#TradeandotherpayablesMovementinthesalesrebatesandreservesDetails"/>
  <link:definitionLink xlink:role="http://www.argenx.com/role/TradeandotherpayablesMovementinthesalesrebatesandreservesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_DisclosureOfSignificantInvestmentsInSubsidiariesLineItems_adda07b6-a3b6-40a3-8342-4bd31442fd6c" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_DisclosureOfSignificantInvestmentsInSubsidiariesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_DisclosureOfSignificantInvestmentsInSubsidiariesTable_3170fd4d-1e16-4c97-b36a-2e0d905a7749" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_DisclosureOfSignificantInvestmentsInSubsidiariesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_ifrs-full_DisclosureOfSignificantInvestmentsInSubsidiariesLineItems_adda07b6-a3b6-40a3-8342-4bd31442fd6c" xlink:to="loc_ifrs-full_DisclosureOfSignificantInvestmentsInSubsidiariesTable_3170fd4d-1e16-4c97-b36a-2e0d905a7749" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_789183dc-650b-421b-bd6e-f77f7692f6b0" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ifrs-full_DisclosureOfSignificantInvestmentsInSubsidiariesTable_3170fd4d-1e16-4c97-b36a-2e0d905a7749" xlink:to="loc_srt_ProductOrServiceAxis_789183dc-650b-421b-bd6e-f77f7692f6b0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_789183dc-650b-421b-bd6e-f77f7692f6b0_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_789183dc-650b-421b-bd6e-f77f7692f6b0" xlink:to="loc_srt_ProductsAndServicesDomain_789183dc-650b-421b-bd6e-f77f7692f6b0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_9ebf993a-7c77-4a21-aae8-e95ecc8cb747" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_789183dc-650b-421b-bd6e-f77f7692f6b0" xlink:to="loc_srt_ProductsAndServicesDomain_9ebf993a-7c77-4a21-aae8-e95ecc8cb747" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_RebatesAndChargeBacksMember_f524cd53-268f-437b-b1b0-7abd262284e7" xlink:href="argx-20260630.xsd#argx_RebatesAndChargeBacksMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_9ebf993a-7c77-4a21-aae8-e95ecc8cb747" xlink:to="loc_argx_RebatesAndChargeBacksMember_f524cd53-268f-437b-b1b0-7abd262284e7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_DistributionFeesAndProductReturnsMember_a86590ac-dd37-463e-894a-36a7bba328df" xlink:href="argx-20260630.xsd#argx_DistributionFeesAndProductReturnsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_9ebf993a-7c77-4a21-aae8-e95ecc8cb747" xlink:to="loc_argx_DistributionFeesAndProductReturnsMember_a86590ac-dd37-463e-894a-36a7bba328df" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_Accruals_11b2bcd0-d321-43f0-8a0e-e56a7afe23c0" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_Accruals"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfSignificantInvestmentsInSubsidiariesLineItems_adda07b6-a3b6-40a3-8342-4bd31442fd6c" xlink:to="loc_ifrs-full_Accruals_11b2bcd0-d321-43f0-8a0e-e56a7afe23c0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_AccrualsIncreaseFromSales_5beb0c96-d2c3-4e0c-9300-06f6321846bd" xlink:href="argx-20260630.xsd#argx_AccrualsIncreaseFromSales"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfSignificantInvestmentsInSubsidiariesLineItems_adda07b6-a3b6-40a3-8342-4bd31442fd6c" xlink:to="loc_argx_AccrualsIncreaseFromSales_5beb0c96-d2c3-4e0c-9300-06f6321846bd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_AccrualsIncreaseDecreaseFromPriorPeriodSales_a99e1752-96a7-47c1-a162-4a3cf3878b1c" xlink:href="argx-20260630.xsd#argx_AccrualsIncreaseDecreaseFromPriorPeriodSales"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfSignificantInvestmentsInSubsidiariesLineItems_adda07b6-a3b6-40a3-8342-4bd31442fd6c" xlink:to="loc_argx_AccrualsIncreaseDecreaseFromPriorPeriodSales_a99e1752-96a7-47c1-a162-4a3cf3878b1c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_AccrualsDecreaseFromCreditOrPaymentsRelatedToSales_c2425444-01ba-4272-b918-71a61c11ef9d" xlink:href="argx-20260630.xsd#argx_AccrualsDecreaseFromCreditOrPaymentsRelatedToSales"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfSignificantInvestmentsInSubsidiariesLineItems_adda07b6-a3b6-40a3-8342-4bd31442fd6c" xlink:to="loc_argx_AccrualsDecreaseFromCreditOrPaymentsRelatedToSales_c2425444-01ba-4272-b918-71a61c11ef9d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_AccrualsForeignCurrencyTranslationAdjustment_e45872b5-af58-4f14-8ad1-abf89698b7cc" xlink:href="argx-20260630.xsd#argx_AccrualsForeignCurrencyTranslationAdjustment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfSignificantInvestmentsInSubsidiariesLineItems_adda07b6-a3b6-40a3-8342-4bd31442fd6c" xlink:to="loc_argx_AccrualsForeignCurrencyTranslationAdjustment_e45872b5-af58-4f14-8ad1-abf89698b7cc" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_Accruals_ba702d03-539b-45b2-a70b-c7759cc15400" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_Accruals"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.argenx.com/role/SegmentreportingProductnetsalesbycountryofsalesDetails" xlink:type="simple" xlink:href="argx-20260630.xsd#SegmentreportingProductnetsalesbycountryofsalesDetails"/>
  <link:definitionLink xlink:role="http://www.argenx.com/role/SegmentreportingProductnetsalesbycountryofsalesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_DisclosureOfGeographicalAreasLineItems_cb6820d8-852b-4531-b886-c98607f2ff4b" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_DisclosureOfGeographicalAreasLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_DisclosureOfGeographicalAreasTable_4cb31e2d-a547-420f-904b-580fa4a7702e" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_DisclosureOfGeographicalAreasTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_ifrs-full_DisclosureOfGeographicalAreasLineItems_cb6820d8-852b-4531-b886-c98607f2ff4b" xlink:to="loc_ifrs-full_DisclosureOfGeographicalAreasTable_4cb31e2d-a547-420f-904b-580fa4a7702e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_GeographicalAreasAxis_ed7f6518-d9d9-4e5c-95a0-859c58d7b55c" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_GeographicalAreasAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ifrs-full_DisclosureOfGeographicalAreasTable_4cb31e2d-a547-420f-904b-580fa4a7702e" xlink:to="loc_ifrs-full_GeographicalAreasAxis_ed7f6518-d9d9-4e5c-95a0-859c58d7b55c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_GeographicalAreasDomain_ed7f6518-d9d9-4e5c-95a0-859c58d7b55c_default" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_GeographicalAreasDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_ifrs-full_GeographicalAreasAxis_ed7f6518-d9d9-4e5c-95a0-859c58d7b55c" xlink:to="loc_ifrs-full_GeographicalAreasDomain_ed7f6518-d9d9-4e5c-95a0-859c58d7b55c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_GeographicalAreasDomain_f95d8344-8928-4382-8267-d60e92d789a0" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_GeographicalAreasDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_ifrs-full_GeographicalAreasAxis_ed7f6518-d9d9-4e5c-95a0-859c58d7b55c" xlink:to="loc_ifrs-full_GeographicalAreasDomain_f95d8344-8928-4382-8267-d60e92d789a0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_e21a1bf7-dc71-41b9-8c70-d27b9e454321" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_GeographicalAreasDomain_f95d8344-8928-4382-8267-d60e92d789a0" xlink:to="loc_country_US_e21a1bf7-dc71-41b9-8c70-d27b9e454321" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_JP_d8a7bcc5-7661-41ec-a956-caa9d801faa8" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_JP"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_GeographicalAreasDomain_f95d8344-8928-4382-8267-d60e92d789a0" xlink:to="loc_country_JP_d8a7bcc5-7661-41ec-a956-caa9d801faa8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_CN_3ce47d2d-af49-44a0-9fe1-fb42ca52f84a" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_CN"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_GeographicalAreasDomain_f95d8344-8928-4382-8267-d60e92d789a0" xlink:to="loc_country_CN_3ce47d2d-af49-44a0-9fe1-fb42ca52f84a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_RestOfTheWorldMember_019f5c18-bbe8-7e20-bed8-f07ba34398bf" xlink:href="argx-20260630.xsd#argx_RestOfTheWorldMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_GeographicalAreasDomain_f95d8344-8928-4382-8267-d60e92d789a0" xlink:to="loc_argx_RestOfTheWorldMember_019f5c18-bbe8-7e20-bed8-f07ba34398bf" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_RevenueFromSaleOfGoods_25b62275-8d77-4de5-8e02-825138e5d47e" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_RevenueFromSaleOfGoods"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfGeographicalAreasLineItems_cb6820d8-852b-4531-b886-c98607f2ff4b" xlink:to="loc_ifrs-full_RevenueFromSaleOfGoods_25b62275-8d77-4de5-8e02-825138e5d47e" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.argenx.com/role/RelatedpartytransactionsDetails" xlink:type="simple" xlink:href="argx-20260630.xsd#RelatedpartytransactionsDetails"/>
  <link:definitionLink xlink:role="http://www.argenx.com/role/RelatedpartytransactionsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_DisclosureOfTransactionsBetweenRelatedPartiesLineItems_48bcbfa5-d2cf-4f18-bef9-eab205ce8831" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_DisclosureOfTransactionsBetweenRelatedPartiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_DisclosureOfTransactionsBetweenRelatedPartiesTable_3c589221-22b2-40fd-aa5c-209fbc3ebd37" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_DisclosureOfTransactionsBetweenRelatedPartiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_ifrs-full_DisclosureOfTransactionsBetweenRelatedPartiesLineItems_48bcbfa5-d2cf-4f18-bef9-eab205ce8831" xlink:to="loc_ifrs-full_DisclosureOfTransactionsBetweenRelatedPartiesTable_3c589221-22b2-40fd-aa5c-209fbc3ebd37" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_CategoriesOfRelatedPartiesAxis_93e2d797-3f08-4afd-b256-58385d148dc0" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_CategoriesOfRelatedPartiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ifrs-full_DisclosureOfTransactionsBetweenRelatedPartiesTable_3c589221-22b2-40fd-aa5c-209fbc3ebd37" xlink:to="loc_ifrs-full_CategoriesOfRelatedPartiesAxis_93e2d797-3f08-4afd-b256-58385d148dc0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_CategoriesOfRelatedPartiesDomain_93e2d797-3f08-4afd-b256-58385d148dc0_default" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_CategoriesOfRelatedPartiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_ifrs-full_CategoriesOfRelatedPartiesAxis_93e2d797-3f08-4afd-b256-58385d148dc0" xlink:to="loc_ifrs-full_CategoriesOfRelatedPartiesDomain_93e2d797-3f08-4afd-b256-58385d148dc0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_CategoriesOfRelatedPartiesDomain_460ea4b4-a08d-4a32-a3ad-39816f5eefa0" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_CategoriesOfRelatedPartiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_ifrs-full_CategoriesOfRelatedPartiesAxis_93e2d797-3f08-4afd-b256-58385d148dc0" xlink:to="loc_ifrs-full_CategoriesOfRelatedPartiesDomain_460ea4b4-a08d-4a32-a3ad-39816f5eefa0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ChiefExecutiveOfficerMember_019f26fe-d20b-73cd-ad26-fdc8f1873111" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ChiefExecutiveOfficerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_CategoriesOfRelatedPartiesDomain_460ea4b4-a08d-4a32-a3ad-39816f5eefa0" xlink:to="loc_srt_ChiefExecutiveOfficerMember_019f26fe-d20b-73cd-ad26-fdc8f1873111" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_ExecutiveDirectorsMember_1721e6bd-594a-4a93-a18f-a86d8bf6eb31" xlink:href="argx-20260630.xsd#argx_ExecutiveDirectorsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_CategoriesOfRelatedPartiesDomain_460ea4b4-a08d-4a32-a3ad-39816f5eefa0" xlink:to="loc_argx_ExecutiveDirectorsMember_1721e6bd-594a-4a93-a18f-a86d8bf6eb31" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_NonExecutiveDirectorMember_06e9bec1-8c50-4264-9929-63c8b797cc41" xlink:href="argx-20260630.xsd#argx_NonExecutiveDirectorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_CategoriesOfRelatedPartiesDomain_460ea4b4-a08d-4a32-a3ad-39816f5eefa0" xlink:to="loc_argx_NonExecutiveDirectorMember_06e9bec1-8c50-4264-9929-63c8b797cc41" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsAxis_efd32e3f-01db-4227-99a8-f46ded052671" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_TypesOfSharebasedPaymentArrangementsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_ifrs-full_DisclosureOfTransactionsBetweenRelatedPartiesTable_3c589221-22b2-40fd-aa5c-209fbc3ebd37" xlink:to="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsAxis_efd32e3f-01db-4227-99a8-f46ded052671" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsDomain_efd32e3f-01db-4227-99a8-f46ded052671_default" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_TypesOfSharebasedPaymentArrangementsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsAxis_efd32e3f-01db-4227-99a8-f46ded052671" xlink:to="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsDomain_efd32e3f-01db-4227-99a8-f46ded052671_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsDomain_217fe23a-8064-4320-9e02-b438ca760341" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_TypesOfSharebasedPaymentArrangementsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsAxis_efd32e3f-01db-4227-99a8-f46ded052671" xlink:to="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsDomain_217fe23a-8064-4320-9e02-b438ca760341" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_PerformanceStockUnitsPSUsMember_4dfca6e0-5b36-4851-8545-f607f39481ca" xlink:href="argx-20260630.xsd#argx_PerformanceStockUnitsPSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsDomain_217fe23a-8064-4320-9e02-b438ca760341" xlink:to="loc_argx_PerformanceStockUnitsPSUsMember_4dfca6e0-5b36-4851-8545-f607f39481ca" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_RestrictedShareUnitsMember_019f652d-00cb-7f33-9cb1-4abd5a59eacc" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_RestrictedShareUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_TypesOfSharebasedPaymentArrangementsDomain_217fe23a-8064-4320-9e02-b438ca760341" xlink:to="loc_ifrs-full_RestrictedShareUnitsMember_019f652d-00cb-7f33-9cb1-4abd5a59eacc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_MaximumTermOfOptionsGrantedForShareBasedPaymentArrangement_019f2704-6ba6-7e6f-b042-40bcc55eca46" xlink:href="argx-20260630.xsd#argx_MaximumTermOfOptionsGrantedForShareBasedPaymentArrangement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfTransactionsBetweenRelatedPartiesLineItems_48bcbfa5-d2cf-4f18-bef9-eab205ce8831" xlink:to="loc_argx_MaximumTermOfOptionsGrantedForShareBasedPaymentArrangement_019f2704-6ba6-7e6f-b042-40bcc55eca46" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_PerformanceRequirementsForShareBasedPaymentArrangementPerformancePeriod_019f26fb-4b0f-7094-a0ca-12a4f6ec3b2c" xlink:href="argx-20260630.xsd#argx_PerformanceRequirementsForShareBasedPaymentArrangementPerformancePeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfTransactionsBetweenRelatedPartiesLineItems_48bcbfa5-d2cf-4f18-bef9-eab205ce8831" xlink:to="loc_argx_PerformanceRequirementsForShareBasedPaymentArrangementPerformancePeriod_019f26fb-4b0f-7094-a0ca-12a4f6ec3b2c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_NumberOfShareOptionsGrantedInSharebasedPaymentArrangement_c51454f6-11e5-4a62-8787-bcd137bfbf7e" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_NumberOfShareOptionsGrantedInSharebasedPaymentArrangement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfTransactionsBetweenRelatedPartiesLineItems_48bcbfa5-d2cf-4f18-bef9-eab205ce8831" xlink:to="loc_ifrs-full_NumberOfShareOptionsGrantedInSharebasedPaymentArrangement_c51454f6-11e5-4a62-8787-bcd137bfbf7e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_NumberOfInstrumentsOtherEquityInstrumentsGranted_56571ee1-c74c-41ee-9045-6ae859097469" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_NumberOfInstrumentsOtherEquityInstrumentsGranted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_DisclosureOfTransactionsBetweenRelatedPartiesLineItems_48bcbfa5-d2cf-4f18-bef9-eab205ce8831" xlink:to="loc_ifrs-full_NumberOfInstrumentsOtherEquityInstrumentsGranted_56571ee1-c74c-41ee-9045-6ae859097469" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.argenx.com/role/CommitmentsDetails" xlink:type="simple" xlink:href="argx-20260630.xsd#CommitmentsDetails"/>
  <link:definitionLink xlink:role="http://www.argenx.com/role/CommitmentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_argx_CommitmentsLineItems_7dc88d58-3875-4351-8615-b70577ddf74e" xlink:href="argx-20260630.xsd#argx_CommitmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_CommitmentsTable_c615d5f6-c028-40b9-bd21-918b08526f96" xlink:href="argx-20260630.xsd#argx_CommitmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_argx_CommitmentsLineItems_7dc88d58-3875-4351-8615-b70577ddf74e" xlink:to="loc_argx_CommitmentsTable_c615d5f6-c028-40b9-bd21-918b08526f96" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_CounterpartiesAxis_019efd43-c84c-7cce-a11a-d4b2175e3bff" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_CounterpartiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_argx_CommitmentsTable_c615d5f6-c028-40b9-bd21-918b08526f96" xlink:to="loc_ifrs-full_CounterpartiesAxis_019efd43-c84c-7cce-a11a-d4b2175e3bff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_CounterpartiesDomain_019efd43-c84c-7cce-a11a-d4b2175e3bff_default" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_CounterpartiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_ifrs-full_CounterpartiesAxis_019efd43-c84c-7cce-a11a-d4b2175e3bff" xlink:to="loc_ifrs-full_CounterpartiesDomain_019efd43-c84c-7cce-a11a-d4b2175e3bff_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_CounterpartiesDomain_019efd43-c84c-7fa9-a0b0-66151755832d" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_CounterpartiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_ifrs-full_CounterpartiesAxis_019efd43-c84c-7cce-a11a-d4b2175e3bff" xlink:to="loc_ifrs-full_CounterpartiesDomain_019efd43-c84c-7fa9-a0b0-66151755832d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_HalozymeTherapeuticsIncMember_019efd43-c84c-7602-bbfc-190a57e5acec" xlink:href="argx-20260630.xsd#argx_HalozymeTherapeuticsIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_CounterpartiesDomain_019efd43-c84c-7fa9-a0b0-66151755832d" xlink:to="loc_argx_HalozymeTherapeuticsIncMember_019efd43-c84c-7602-bbfc-190a57e5acec" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_LonzaAndFujifilmMember_019efd43-c84c-7b08-9664-3289d381453a" xlink:href="argx-20260630.xsd#argx_LonzaAndFujifilmMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ifrs-full_CounterpartiesDomain_019efd43-c84c-7fa9-a0b0-66151755832d" xlink:to="loc_argx_LonzaAndFujifilmMember_019efd43-c84c-7b08-9664-3289d381453a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_IfrsTypeOfArrangementAndNonArrangementTransactionsAxis_019efd43-c84c-7517-a804-c6071eb2ac3d" xlink:href="argx-20260630.xsd#argx_IfrsTypeOfArrangementAndNonArrangementTransactionsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_argx_CommitmentsTable_c615d5f6-c028-40b9-bd21-918b08526f96" xlink:to="loc_argx_IfrsTypeOfArrangementAndNonArrangementTransactionsAxis_019efd43-c84c-7517-a804-c6071eb2ac3d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_IfrsTypeOfArrangementAndNonArrangementTransactionsDomain_019efd43-c84c-7517-a804-c6071eb2ac3d_default" xlink:href="argx-20260630.xsd#argx_IfrsTypeOfArrangementAndNonArrangementTransactionsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_argx_IfrsTypeOfArrangementAndNonArrangementTransactionsAxis_019efd43-c84c-7517-a804-c6071eb2ac3d" xlink:to="loc_argx_IfrsTypeOfArrangementAndNonArrangementTransactionsDomain_019efd43-c84c-7517-a804-c6071eb2ac3d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_IfrsTypeOfArrangementAndNonArrangementTransactionsDomain_019efd43-c84c-73fa-a185-ead5eaff9f39" xlink:href="argx-20260630.xsd#argx_IfrsTypeOfArrangementAndNonArrangementTransactionsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_argx_IfrsTypeOfArrangementAndNonArrangementTransactionsAxis_019efd43-c84c-7517-a804-c6071eb2ac3d" xlink:to="loc_argx_IfrsTypeOfArrangementAndNonArrangementTransactionsDomain_019efd43-c84c-73fa-a185-ead5eaff9f39" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_EfgartigimodMember_019efd43-c84c-7495-bf18-5149dd39b7d0" xlink:href="argx-20260630.xsd#argx_EfgartigimodMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_argx_IfrsTypeOfArrangementAndNonArrangementTransactionsDomain_019efd43-c84c-73fa-a185-ead5eaff9f39" xlink:to="loc_argx_EfgartigimodMember_019efd43-c84c-7495-bf18-5149dd39b7d0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_ContractualCommitmentsForAcquisitionOfPropertyPlantAndEquipment_019efd43-c84c-7221-9f8d-f011499bf563" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_ContractualCommitmentsForAcquisitionOfPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_argx_CommitmentsLineItems_7dc88d58-3875-4351-8615-b70577ddf74e" xlink:to="loc_ifrs-full_ContractualCommitmentsForAcquisitionOfPropertyPlantAndEquipment_019efd43-c84c-7221-9f8d-f011499bf563" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ifrs-full_CapitalCommitments_019efd43-c84c-7ba7-94d9-19546222fb9a" xlink:href="https://xbrl.ifrs.org/taxonomy/2025-03-27/full_ifrs/full_ifrs-cor_2025-03-27.xsd#ifrs-full_CapitalCommitments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_argx_CommitmentsLineItems_7dc88d58-3875-4351-8615-b70577ddf74e" xlink:to="loc_ifrs-full_CapitalCommitments_019efd43-c84c-7ba7-94d9-19546222fb9a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_FutureMilestonePaymentsAllTargets_019efd43-c84c-74dc-8f90-e448f391a417" xlink:href="argx-20260630.xsd#argx_FutureMilestonePaymentsAllTargets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_argx_CommitmentsLineItems_7dc88d58-3875-4351-8615-b70577ddf74e" xlink:to="loc_argx_FutureMilestonePaymentsAllTargets_019efd43-c84c-74dc-8f90-e448f391a417" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_argx_NumberOnNominatedTargetUnderAgreement_019efd43-c84c-7a02-b4f1-9ee2df3633e7" xlink:href="argx-20260630.xsd#argx_NumberOnNominatedTargetUnderAgreement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_argx_CommitmentsLineItems_7dc88d58-3875-4351-8615-b70577ddf74e" xlink:to="loc_argx_NumberOnNominatedTargetUnderAgreement_019efd43-c84c-7a02-b4f1-9ee2df3633e7" xlink:type="arc" order="3"/>
  </link:definitionLink>
</link:linkbase>
