diff --git a/clang/include/clang-c/Index.h b/clang/include/clang-c/Index.h
--- a/clang/include/clang-c/Index.h
+++ b/clang/include/clang-c/Index.h
@@ -2189,7 +2189,17 @@
    */
   CXCursor_CXXAddrspaceCastExpr = 152,
 
-  CXCursor_LastExpr = CXCursor_CXXAddrspaceCastExpr,
+  /**
+   * Expression that references a C++20 concept.
+   */
+  CXCursor_ConceptSpecializationExpr = 153,
+
+  /**
+   * Expression that references a C++20 concept.
+   */
+  CXCursor_RequiresExpr = 154,
+
+  CXCursor_LastExpr = CXCursor_RequiresExpr,
 
   /* Statements */
   CXCursor_FirstStmt = 200,
@@ -2700,8 +2710,13 @@
    * a friend declaration.
    */
   CXCursor_FriendDecl = 603,
+  /**
+   * a concept declaration.
+   */
+  CXCursor_ConceptDecl = 604,
+
   CXCursor_FirstExtraDecl = CXCursor_ModuleImportDecl,
-  CXCursor_LastExtraDecl = CXCursor_FriendDecl,
+  CXCursor_LastExtraDecl = CXCursor_ConceptDecl,
 
   /**
    * A code completion overload candidate.
@@ -6319,7 +6334,8 @@
   CXIdxEntity_CXXDestructor = 23,
   CXIdxEntity_CXXConversionFunction = 24,
   CXIdxEntity_CXXTypeAlias = 25,
-  CXIdxEntity_CXXInterface = 26
+  CXIdxEntity_CXXInterface = 26,
+  CXIdxEntity_CXXConcept = 27
 
 } CXIdxEntityKind;
 
diff --git a/clang/lib/Sema/SemaCodeComplete.cpp b/clang/lib/Sema/SemaCodeComplete.cpp
--- a/clang/lib/Sema/SemaCodeComplete.cpp
+++ b/clang/lib/Sema/SemaCodeComplete.cpp
@@ -4044,6 +4044,9 @@
   case Decl::ObjCTypeParam:
     return CXCursor_TemplateTypeParameter;
 
+  case Decl::Concept:
+    return CXCursor_ConceptDecl;
+
   default:
     if (const auto *TD = dyn_cast<TagDecl>(D)) {
       switch (TD->getTagKind()) {
diff --git a/clang/test/Index/index-concept-kind.cpp b/clang/test/Index/index-concept-kind.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/Index/index-concept-kind.cpp
@@ -0,0 +1,9 @@
+// RUN: c-index-test -index-file %s -std=gnu++20 | FileCheck %s
+
+template <typename T>
+concept LargeType = sizeof(T) > 8;
+// CHECK: [indexDeclaration]: kind: concept | name: LargeType | USR: c:@CT@LargeType | lang: C | cursor: ConceptDecl=LargeType:[[@LINE-1]]:9 (Definition) | loc: [[@LINE-1]]:9 | semantic-container: [TU] | lexical-container: [TU] | isRedecl: 0 | isDef: 1 | isContainer: 0 | isImplicit: 0
+
+template <LargeType T>
+// CHECK: [indexEntityReference]: kind: concept | name: LargeType | USR: c:@CT@LargeType | lang: C | cursor: TemplateRef=LargeType:4:9 | loc: [[@LINE-1]]:11 | <parent>:: kind: function-template | name: f | USR: c:@FT@>1#Tf#v# | lang: C++ | container: [<<NULL>>] | refkind: direct | role: ref
+void f();
diff --git a/clang/test/Index/index-concepts.cpp b/clang/test/Index/index-concepts.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/Index/index-concepts.cpp
@@ -0,0 +1,186 @@
+// RUN: c-index-test -test-load-source all %s -std=gnu++20 -fno-delayed-template-parsing | FileCheck %s
+
+template<class T>
+struct type_trait {
+    const static bool value = false;
+};
+
+template<>
+struct type_trait<int> {
+    const static bool value = true;
+};
+
+template <class T>
+requires (type_trait<T>::value)
+// CHECK: index-concepts.cpp:[[@LINE-1]]:10: ParenExpr= Extent=[[[@LINE-1]]:10 - [[@LINE-1]]:32]
+// CHECK: index-concepts.cpp:[[@LINE-2]]:11: DeclRefExpr= Extent=[[[@LINE-2]]:11 - [[@LINE-2]]:31]
+// CHECK: index-concepts.cpp:[[@LINE-3]]:11: TemplateRef=type_trait:4:8 Extent=[[[@LINE-3]]:11 - [[@LINE-3]]:21]
+// CHECK: index-concepts.cpp:[[@LINE-4]]:22: TypeRef=T:13:17 Extent=[[[@LINE-4]]:22 - [[@LINE-4]]:23]
+void indexRequiresClause() {
+}
+
+template<class T>
+requires (type_trait<T>::value)
+// CHECK: index-concepts.cpp:[[@LINE-1]]:10: ParenExpr= Extent=[[[@LINE-1]]:10 - [[@LINE-1]]:32]
+// CHECK: index-concepts.cpp:[[@LINE-2]]:11: DeclRefExpr= Extent=[[[@LINE-2]]:11 - [[@LINE-2]]:31]
+// CHECK: index-concepts.cpp:[[@LINE-3]]:11: TemplateRef=type_trait:4:8 Extent=[[[@LINE-3]]:11 - [[@LINE-3]]:21]
+// CHECK: index-concepts.cpp:[[@LINE-4]]:22: TypeRef=T:22:16 Extent=[[[@LINE-4]]:22 - [[@LINE-4]]:23]
+class IndexRequiresClauseInClass {};
+
+template <class T>
+concept Con1 = type_trait<T>::value;
+// CHECK: index-concepts.cpp:[[@LINE-1]]:9: ConceptDecl=Con1:[[@LINE-1]]:9 (Definition) Extent=[[[@LINE-2]]:1 - [[@LINE-1]]:36]
+// CHECK: index-concepts.cpp:[[@LINE-3]]:17: TemplateTypeParameter=T:[[@LINE-3]]:17 (Definition) Extent=[[[@LINE-3]]:11 - [[@LINE-3]]:18] [access=public]
+// CHECK: index-concepts.cpp:[[@LINE-3]]:16: DeclRefExpr= Extent=[[[@LINE-3]]:16 - [[@LINE-3]]:36]
+// CHECK: index-concepts.cpp:[[@LINE-4]]:16: TemplateRef=type_trait:4:8 Extent=[[[@LINE-4]]:16 - [[@LINE-4]]:26]
+// CHECK: index-concepts.cpp:[[@LINE-5]]:27: TypeRef=T:30:17 Extent=[[[@LINE-5]]:27 - [[@LINE-5]]:28]
+
+constexpr int sizeFunc() { return 4; }
+
+template <class T>
+concept ConWithLogicalAnd = Con1<T> && sizeof(T) > sizeFunc();
+// CHECK: index-concepts.cpp:[[@LINE-1]]:9: ConceptDecl=ConWithLogicalAnd:[[@LINE-1]]:9 (Definition) Extent=[[[@LINE-2]]:1 - [[@LINE-1]]:62]
+// CHECK: index-concepts.cpp:[[@LINE-3]]:17: TemplateTypeParameter=T:[[@LINE-3]]:17 (Definition) Extent=[[[@LINE-3]]:11 - [[@LINE-3]]:18] [access=public]
+// CHECK: index-concepts.cpp:[[@LINE-3]]:29: BinaryOperator= Extent=[[[@LINE-3]]:29 - [[@LINE-3]]:62]
+// CHECK: index-concepts.cpp:[[@LINE-4]]:29: ConceptSpecializationExpr= Extent=[[[@LINE-4]]:29 - [[@LINE-4]]:36]
+// CHECK: index-concepts.cpp:[[@LINE-5]]:29: TemplateRef=Con1:31:9 Extent=[[[@LINE-5]]:29 - [[@LINE-5]]:33]
+// CHECK: index-concepts.cpp:[[@LINE-6]]:40: BinaryOperator= Extent=[[[@LINE-6]]:40 - [[@LINE-6]]:62]
+// CHECK: index-concepts.cpp:[[@LINE-7]]:40: UnaryExpr= Extent=[[[@LINE-7]]:40 - [[@LINE-7]]:49]
+// CHECK: index-concepts.cpp:[[@LINE-8]]:47: TypeRef=T:40:17 Extent=[[[@LINE-8]]:47 - [[@LINE-8]]:48]
+// CHECK: index-concepts.cpp:[[@LINE-9]]:52: UnexposedExpr=sizeFunc:38:15 Extent=[[[@LINE-9]]:52 - [[@LINE-9]]:62]
+// CHECK: index-concepts.cpp:[[@LINE-10]]:52: CallExpr=sizeFunc:38:15 Extent=[[[@LINE-10]]:52 - [[@LINE-10]]:62]
+// CHECK: index-concepts.cpp:[[@LINE-11]]:52: UnexposedExpr=sizeFunc:38:15 Extent=[[[@LINE-11]]:52 - [[@LINE-11]]:60]
+// CHECK: index-concepts.cpp:[[@LINE-12]]:52: DeclRefExpr=sizeFunc:38:15 Extent=[[[@LINE-12]]:52 - [[@LINE-12]]:60]
+
+namespace ns {
+
+template <class T>
+concept ConInNamespace = sizeof(T) > 4;
+
+}
+
+template <class T1, class T2>
+concept ConTwoTemplateParams = ns::ConInNamespace<T1> && ConWithLogicalAnd<T2>;
+// CHECK: index-concepts.cpp:[[@LINE-1]]:9: ConceptDecl=ConTwoTemplateParams:[[@LINE-1]]:9 (Definition) Extent=[[[@LINE-2]]:1 - [[@LINE-1]]:79]
+// CHECK: index-concepts.cpp:[[@LINE-3]]:17: TemplateTypeParameter=T1:[[@LINE-3]]:17 (Definition) Extent=[[[@LINE-3]]:11 - [[@LINE-3]]:19] [access=public]
+// CHECK: index-concepts.cpp:[[@LINE-4]]:27: TemplateTypeParameter=T2:[[@LINE-4]]:27 (Definition) Extent=[[[@LINE-4]]:21 - [[@LINE-4]]:29] [access=public]
+// CHECK: index-concepts.cpp:[[@LINE-4]]:36: BinaryOperator= Extent=[[[@LINE-4]]:36 - [[@LINE-4]]:79]
+// CHECK: index-concepts.cpp:[[@LINE-5]]:36: ConceptSpecializationExpr= Extent=[[[@LINE-5]]:36 - [[@LINE-5]]:54]
+// CHECK: index-concepts.cpp:[[@LINE-6]]:32: NamespaceRef=ns:55:11 Extent=[[[@LINE-6]]:32 - [[@LINE-6]]:34]
+// CHECK: index-concepts.cpp:[[@LINE-7]]:36: TemplateRef=ConInNamespace:58:9 Extent=[[[@LINE-7]]:36 - [[@LINE-7]]:50]
+// CHECK: index-concepts.cpp:[[@LINE-8]]:58: ConceptSpecializationExpr= Extent=[[[@LINE-8]]:58 - [[@LINE-8]]:79]
+// CHECK: index-concepts.cpp:[[@LINE-9]]:58: TemplateRef=ConWithLogicalAnd:41:9 Extent=[[[@LINE-9]]:58 - [[@LINE-9]]:75]
+
+
+struct ConcreteType {};
+
+template<class T>
+requires ConTwoTemplateParams<T, ConcreteType>
+struct UsesConceptInRequires {};
+// CHECK: index-concepts.cpp:[[@LINE-1]]:8: ClassTemplate=UsesConceptInRequires:[[@LINE-1]]:8 (Definition) Extent=[[[@LINE-3]]:1 - [[@LINE-1]]:32]
+// CHECK: index-concepts.cpp:[[@LINE-4]]:16: TemplateTypeParameter=T:[[@LINE-4]]:16 (Definition) Extent=[[[@LINE-4]]:10 - [[@LINE-4]]:17] [access=public]
+// CHECK: index-concepts.cpp:[[@LINE-4]]:10: ConceptSpecializationExpr= Extent=[[[@LINE-4]]:10 - [[@LINE-4]]:47]
+// CHECK: index-concepts.cpp:[[@LINE-5]]:10: TemplateRef=ConTwoTemplateParams:63:9 Extent=[[[@LINE-5]]:10 - [[@LINE-5]]:30]
+// CHECK: index-concepts.cpp:[[@LINE-6]]:31: TypeRef=T:[[@LINE-7]]:16 Extent=[[[@LINE-6]]:31 - [[@LINE-6]]:32]
+// CHECK: index-concepts.cpp:[[@LINE-7]]:34: TypeRef=struct ConcreteType:[[@LINE-10]]:8 Extent=[[[@LINE-7]]:34 - [[@LINE-7]]:46]
+
+
+template<ConWithLogicalAnd T>
+struct UsesConceptInTemplateArg {};
+// CHECK: index-concepts.cpp:[[@LINE-1]]:8: ClassTemplate=UsesConceptInTemplateArg:[[@LINE-1]]:8 (Definition) Extent=[[[@LINE-2]]:1 - [[@LINE-1]]:35]
+// CHECK: index-concepts.cpp:[[@LINE-3]]:28: TemplateTypeParameter=T:[[@LINE-3]]:28 (Definition) Extent=[[[@LINE-3]]:10 - [[@LINE-3]]:29] [access=public]
+// CHECK: index-concepts.cpp:[[@LINE-4]]:10: TemplateRef=ConWithLogicalAnd:41:9 Extent=[[[@LINE-4]]:10 - [[@LINE-4]]:27]
+
+void usesConceptInAutoParam(ns::ConInNamespace auto x) {}
+// CHECK: index-concepts.cpp:[[@LINE-1]]:6: FunctionTemplate=usesConceptInAutoParam:[[@LINE-1]]:6 (Definition)
+// CHECK: index-concepts.cpp:[[@LINE-2]]:53: ParmDecl=x:[[@LINE-2]]:53 (Definition) Extent=[[[@LINE-2]]:29 - [[@LINE-2]]:54]
+// CHECK: index-concepts.cpp:[[@LINE-3]]:29: NamespaceRef=ns:55:11 Extent=[[[@LINE-3]]:29 - [[@LINE-3]]:31]
+// CHECK: index-concepts.cpp:[[@LINE-4]]:33: TemplateRef=ConInNamespace:58:9 Extent=[[[@LINE-4]]:33 - [[@LINE-4]]:47]
+// CHECK: index-concepts.cpp:[[@LINE-5]]:48: TypeRef=ns::ConInNamespace auto:[[@LINE-5]]:53 Extent=[[[@LINE-5]]:48 - [[@LINE-5]]:52]
+// CHECK: index-concepts.cpp:[[@LINE-6]]:56: CompoundStmt= Extent=[[[@LINE-6]]:56 - [[@LINE-6]]:58]
+
+
+template<class T>
+void testTrailingRequires(const T &x)
+requires ns::ConInNamespace<T> && ConTwoTemplateParams<T, ConcreteType> {}
+// CHECK: index-concepts.cpp:[[@LINE-2]]:6: FunctionTemplate=testTrailingRequires:[[@LINE-2]]:6 (Definition) Extent=[[[@LINE-3]]:1 - [[@LINE-1]]:75]
+// CHECK: index-concepts.cpp:[[@LINE-4]]:16: TemplateTypeParameter=T:[[@LINE-4]]:16 (Definition) Extent=[[[@LINE-4]]:10 - [[@LINE-4]]:17] [access=public]
+// CHECK: index-concepts.cpp:[[@LINE-4]]:36: ParmDecl=x:[[@LINE-4]]:36 (Definition) Extent=[[[@LINE-4]]:27 - [[@LINE-4]]:37]
+// CHECK: index-concepts.cpp:[[@LINE-5]]:33: TypeRef=T:[[@LINE-6]]:16 Extent=[[[@LINE-5]]:33 - [[@LINE-5]]:34]
+// CHECK: index-concepts.cpp:[[@LINE-5]]:14: ConceptSpecializationExpr= Extent=[[[@LINE-5]]:14 - [[@LINE-5]]:31]
+// CHECK: index-concepts.cpp:[[@LINE-6]]:10: NamespaceRef=ns:55:11 Extent=[[[@LINE-6]]:10 - [[@LINE-6]]:12]
+// CHECK: index-concepts.cpp:[[@LINE-7]]:14: TemplateRef=ConInNamespace:58:9 Extent=[[[@LINE-7]]:14 - [[@LINE-7]]:28]
+// CHECK: index-concepts.cpp:[[@LINE-8]]:29: TypeRef=T:[[@LINE-10]]:16 Extent=[[[@LINE-8]]:29 - [[@LINE-8]]:30]
+// CHECK: index-concepts.cpp:[[@LINE-9]]:35: ConceptSpecializationExpr= Extent=[[[@LINE-9]]:35 - [[@LINE-9]]:72]
+// CHECK: index-concepts.cpp:[[@LINE-10]]:35: TemplateRef=ConTwoTemplateParams:63:9 Extent=[[[@LINE-10]]:35 - [[@LINE-10]]:55]
+// CHECK: index-concepts.cpp:[[@LINE-11]]:56: TypeRef=T:[[@LINE-13]]:16 Extent=[[[@LINE-11]]:56 - [[@LINE-11]]:57]
+// CHECK: index-concepts.cpp:[[@LINE-12]]:59: TypeRef=struct ConcreteType:75:8 Extent=[[[@LINE-12]]:59 - [[@LINE-12]]:71]
+
+
+void concreteFunc(ConcreteType);
+
+template<class T>
+void genericFunc(const T&x);
+
+template<class T>
+concept ConWithRequires = requires(const T& x, ConcreteType value) {
+  concreteFunc(value);
+  genericFunc(x);
+};
+// CHECK: index-concepts.cpp:[[@LINE-4]]:9: ConceptDecl=ConWithRequires:[[@LINE-4]]:9 (Definition) Extent=[[[@LINE-5]]:1 - [[@LINE-1]]:2]
+// CHECK: index-concepts.cpp:[[@LINE-6]]:16: TemplateTypeParameter=T:[[@LINE-6]]:16 (Definition) Extent=[[[@LINE-6]]:10 - [[@LINE-6]]:17] [access=public]
+// CHECK: index-concepts.cpp:[[@LINE-6]]:27: RequiresExpr= Extent=[[[@LINE-6]]:27 - [[@LINE-3]]:2]
+// CHECK: index-concepts.cpp:[[@LINE-7]]:61: ParmDecl=value:[[@LINE-7]]:61 (Definition) Extent=[[[@LINE-7]]:48 - [[@LINE-7]]:66]
+// CHECK: index-concepts.cpp:[[@LINE-8]]:48: TypeRef=struct ConcreteType:75:8 Extent=[[[@LINE-8]]:48 - [[@LINE-8]]:60]
+// CHECK: index-concepts.cpp:[[@LINE-9]]:45: ParmDecl=x:[[@LINE-9]]:45 (Definition) Extent=[[[@LINE-9]]:36 - [[@LINE-9]]:46]
+// CHECK: index-concepts.cpp:[[@LINE-10]]:42: TypeRef=T:[[@LINE-11]]:16 Extent=[[[@LINE-10]]:42 - [[@LINE-10]]:43]
+// CHECK: index-concepts.cpp:[[@LINE-10]]:3: UnexposedExpr=concreteFunc:[[@LINE-17]]:6 Extent=[[[@LINE-10]]:3 - [[@LINE-10]]:15]
+// CHECK: index-concepts.cpp:[[@LINE-11]]:3: DeclRefExpr=concreteFunc:[[@LINE-18]]:6 Extent=[[[@LINE-11]]:3 - [[@LINE-11]]:15]
+// CHECK: index-concepts.cpp:[[@LINE-12]]:16: CallExpr=ConcreteType:75:8 Extent=[[[@LINE-12]]:16 - [[@LINE-12]]:21]
+// CHECK: index-concepts.cpp:[[@LINE-13]]:16: UnexposedExpr=value:[[@LINE-14]]:61 Extent=[[[@LINE-13]]:16 - [[@LINE-13]]:21]
+// CHECK: index-concepts.cpp:[[@LINE-14]]:16: DeclRefExpr=value:[[@LINE-15]]:61 Extent=[[[@LINE-14]]:16 - [[@LINE-14]]:21]
+// CHECK: index-concepts.cpp:[[@LINE-14]]:3: DeclRefExpr=[[[@LINE-19]]:6] Extent=[[[@LINE-14]]:3 - [[@LINE-14]]:14]
+// CHECK: index-concepts.cpp:[[@LINE-15]]:3: OverloadedDeclRef=genericFunc[[[@LINE-20]]:6] Extent=[[[@LINE-15]]:3 - [[@LINE-15]]:14]
+// CHECK: index-concepts.cpp:[[@LINE-16]]:15: DeclRefExpr=x:[[@LINE-18]]:45 Extent=[[[@LINE-16]]:15 - [[@LINE-16]]:16]
+
+template<class T>
+concept ConWithCompRequires = requires {
+  { genericFunc(T()) } -> ns::ConInNamespace;
+  { genericFunc(T()) } -> ConTwoTemplateParams<ConcreteType>;
+};
+// CHECK: index-concepts.cpp:[[@LINE-4]]:9: ConceptDecl=ConWithCompRequires:[[@LINE-4]]:9 (Definition) Extent=[[[@LINE-5]]:1 - [[@LINE-1]]:2]
+// CHECK: index-concepts.cpp:[[@LINE-6]]:16: TemplateTypeParameter=T:[[@LINE-6]]:16 (Definition) Extent=[[[@LINE-6]]:10 - [[@LINE-6]]:17] [access=public]
+// CHECK: index-concepts.cpp:[[@LINE-6]]:31: RequiresExpr= Extent=[[[@LINE-6]]:31 - [[@LINE-3]]:2]
+// CHECK: index-concepts.cpp:[[@LINE-6]]:5: DeclRefExpr=[123:6] Extent=[[[@LINE-6]]:5 - [[@LINE-6]]:16]
+// CHECK: index-concepts.cpp:[[@LINE-7]]:5: OverloadedDeclRef=genericFunc[123:6] Extent=[[[@LINE-7]]:5 - [[@LINE-7]]:16]
+// CHECK: index-concepts.cpp:[[@LINE-8]]:17: CallExpr= Extent=[[[@LINE-8]]:17 - [[@LINE-8]]:20]
+// CHECK: index-concepts.cpp:[[@LINE-9]]:17: TypeRef=T:[[@LINE-11]]:16 Extent=[[[@LINE-9]]:17 - [[@LINE-9]]:18]
+// CHECK: index-concepts.cpp:[[@LINE-10]]:27: NamespaceRef=ns:55:11 Extent=[[[@LINE-10]]:27 - [[@LINE-10]]:29]
+// CHECK: index-concepts.cpp:[[@LINE-11]]:31: TemplateRef=ConInNamespace:58:9 Extent=[[[@LINE-11]]:31 - [[@LINE-11]]:45]
+// CHECK: index-concepts.cpp:[[@LINE-11]]:5: DeclRefExpr=[123:6] Extent=[[[@LINE-11]]:5 - [[@LINE-11]]:16]
+// CHECK: index-concepts.cpp:[[@LINE-12]]:5: OverloadedDeclRef=genericFunc[123:6] Extent=[[[@LINE-12]]:5 - [[@LINE-12]]:16]
+// CHECK: index-concepts.cpp:[[@LINE-13]]:17: CallExpr= Extent=[[[@LINE-13]]:17 - [[@LINE-13]]:20]
+// CHECK: index-concepts.cpp:[[@LINE-14]]:17: TypeRef=T:[[@LINE-17]]:16 Extent=[[[@LINE-14]]:17 - [[@LINE-14]]:18]
+// CHECK: index-concepts.cpp:[[@LINE-15]]:27: TemplateRef=ConTwoTemplateParams:63:9 Extent=[[[@LINE-15]]:27 - [[@LINE-15]]:47]
+// CHECK: index-concepts.cpp:[[@LINE-16]]:48: TypeRef=struct ConcreteType:75:8 Extent=[[[@LINE-16]]:48 - [[@LINE-16]]:60]
+
+template<class T>
+concept ConWithTypeReq = requires {
+  typename type_trait<T>;
+};
+// CHECK: index-concepts.cpp:[[@LINE-3]]:9: ConceptDecl=ConWithTypeReq:[[@LINE-3]]:9 (Definition) Extent=[[[@LINE-4]]:1 - [[@LINE-1]]:2]
+// CHECK: index-concepts.cpp:[[@LINE-5]]:16: TemplateTypeParameter=T:[[@LINE-5]]:16 (Definition) Extent=[[[@LINE-5]]:10 - [[@LINE-5]]:17] [access=public]
+// CHECK: index-concepts.cpp:[[@LINE-5]]:26: RequiresExpr= Extent=[[[@LINE-5]]:26 - [[@LINE-3]]:2]
+// CHECK: index-concepts.cpp:[[@LINE-5]]:12: TemplateRef=type_trait:4:8 Extent=[[[@LINE-5]]:12 - [[@LINE-5]]:22]
+// CHECK: index-concepts.cpp:[[@LINE-6]]:23: TypeRef=T:[[@LINE-8]]:16 Extent=[[[@LINE-6]]:23 - [[@LINE-6]]:24]
+
+template<class T>
+concept ConWithNestedReq = requires {
+  requires ns::ConInNamespace<T>;
+};
+// CHECK: index-concepts.cpp:[[@LINE-3]]:9: ConceptDecl=ConWithNestedReq:[[@LINE-3]]:9 (Definition) Extent=[[[@LINE-4]]:1 - [[@LINE-1]]:2]
+// CHECK: index-concepts.cpp:[[@LINE-5]]:16: TemplateTypeParameter=T:[[@LINE-5]]:16 (Definition) Extent=[[[@LINE-5]]:10 - [[@LINE-5]]:17] [access=public]
+// CHECK: index-concepts.cpp:[[@LINE-5]]:28: RequiresExpr= Extent=[[[@LINE-5]]:28 - [[@LINE-3]]:2]
+// CHECK: index-concepts.cpp:[[@LINE-5]]:12: NamespaceRef=ns:55:11 Extent=[[[@LINE-5]]:12 - [[@LINE-5]]:14]
+// CHECK: index-concepts.cpp:[[@LINE-6]]:16: TemplateRef=ConInNamespace:58:9 Extent=[[[@LINE-6]]:16 - [[@LINE-6]]:30]
+// CHECK: index-concepts.cpp:[[@LINE-7]]:31: TypeRef=T:[[@LINE-9]]:16 Extent=[[[@LINE-7]]:31 - [[@LINE-7]]:32]
diff --git a/clang/tools/c-index-test/c-index-test.c b/clang/tools/c-index-test/c-index-test.c
--- a/clang/tools/c-index-test/c-index-test.c
+++ b/clang/tools/c-index-test/c-index-test.c
@@ -3504,6 +3504,8 @@
   case CXIdxEntity_CXXConversionFunction: return "conversion-func";
   case CXIdxEntity_CXXTypeAlias: return "type-alias";
   case CXIdxEntity_CXXInterface: return "c++-__interface";
+  case CXIdxEntity_CXXConcept:
+    return "concept";
   }
   assert(0 && "Garbage entity kind");
   return 0;
diff --git a/clang/tools/libclang/CIndex.cpp b/clang/tools/libclang/CIndex.cpp
--- a/clang/tools/libclang/CIndex.cpp
+++ b/clang/tools/libclang/CIndex.cpp
@@ -761,10 +761,10 @@
 }
 
 bool CursorVisitor::VisitTemplateTypeParmDecl(TemplateTypeParmDecl *D) {
-  if (const auto *TC = D->getTypeConstraint())
-    if (Visit(MakeCXCursor(TC->getImmediatelyDeclaredConstraint(), StmtParent,
-                           TU, RegionOfInterest)))
+  if (const auto *TC = D->getTypeConstraint()) {
+    if (VisitTypeConstraint(*TC))
       return true;
+  }
 
   // Visit the default argument.
   if (D->hasDefaultArgument() && !D->defaultArgumentWasInherited())
@@ -863,6 +863,11 @@
     // FIXME: Attributes?
   }
 
+  if (auto *E = ND->getTrailingRequiresClause()) {
+    if (Visit(E))
+      return true;
+  }
+
   if (ND->doesThisDeclarationHaveABody() && !ND->isLateTemplateParsed()) {
     if (CXXConstructorDecl *Constructor = dyn_cast<CXXConstructorDecl>(ND)) {
       // Find the initializers that were written in the source.
@@ -1310,6 +1315,75 @@
   return VisitVarDecl(D);
 }
 
+bool CursorVisitor::VisitConceptDecl(ConceptDecl *D) {
+  if (VisitTemplateParameters(D->getTemplateParameters()))
+    return true;
+
+  if (auto *E = D->getConstraintExpr()) {
+    if (Visit(MakeCXCursor(E, D, TU, RegionOfInterest)))
+      return true;
+  }
+  return false;
+}
+
+bool CursorVisitor::VisitTypeConstraint(const TypeConstraint &TC) {
+  if (TC.getNestedNameSpecifierLoc()) {
+    if (VisitNestedNameSpecifierLoc(TC.getNestedNameSpecifierLoc()))
+      return true;
+  }
+  if (TC.getNamedConcept()) {
+    if (Visit(MakeCursorTemplateRef(TC.getNamedConcept(),
+                                    TC.getConceptNameLoc(), TU)))
+      return true;
+  }
+  if (auto Args = TC.getTemplateArgsAsWritten()) {
+    for (const auto &Arg : Args->arguments()) {
+      if (VisitTemplateArgumentLoc(Arg))
+        return true;
+    }
+  }
+  return false;
+}
+
+bool CursorVisitor::VisitConceptRequirement(const concepts::Requirement &R) {
+  using namespace concepts;
+  switch (R.getKind()) {
+  case Requirement::RK_Type: {
+    const TypeRequirement &TR = cast<TypeRequirement>(R);
+    if (!TR.isSubstitutionFailure()) {
+      if (Visit(TR.getType()->getTypeLoc()))
+        return true;
+    }
+    break;
+  }
+  case Requirement::RK_Simple:
+  case Requirement::RK_Compound: {
+    const ExprRequirement &ER = cast<ExprRequirement>(R);
+    if (!ER.isExprSubstitutionFailure()) {
+      if (Visit(ER.getExpr()))
+        return true;
+    }
+    if (ER.getKind() == Requirement::RK_Compound) {
+      const auto &RTR = ER.getReturnTypeRequirement();
+      if (RTR.isTypeConstraint()) {
+        if (const auto *Cons = RTR.getTypeConstraint())
+          VisitTypeConstraint(*Cons);
+      }
+    }
+    break;
+  }
+  case Requirement::RK_Nested: {
+    const NestedRequirement &NR = cast<NestedRequirement>(R);
+    if (!NR.isSubstitutionFailure()) {
+      if (Visit(NR.getConstraintExpr()))
+        return true;
+    }
+    break;
+  }
+  }
+  return false;
+}
+
 bool CursorVisitor::VisitDeclarationNameInfo(DeclarationNameInfo Name) {
   switch (Name.getName().getNameKind()) {
   case clang::DeclarationName::Identifier:
@@ -1436,6 +1510,12 @@
       return true;
   }
 
+  if (const auto *E = Params->getRequiresClause()) {
+    if (Visit(MakeCXCursor(Params->getRequiresClause(), nullptr, TU,
+                           RegionOfInterest)))
+      return true;
+  }
+
   return false;
 }
 
@@ -1594,6 +1674,11 @@
 }
 
 bool CursorVisitor::VisitTemplateTypeParmTypeLoc(TemplateTypeParmTypeLoc TL) {
+  if (const auto *TC = TL.getDecl()->getTypeConstraint()) {
+    if (VisitTypeConstraint(*TC))
+      return true;
+  }
+
   return Visit(MakeCursorTypeRef(TL.getDecl(), TL.getNameLoc(), TU));
 }
 
@@ -1869,6 +1954,9 @@
 DEF_JOB(OverloadExprParts, OverloadExpr, OverloadExprPartsKind)
 DEF_JOB(SizeOfPackExprParts, SizeOfPackExpr, SizeOfPackExprPartsKind)
 DEF_JOB(LambdaExprParts, LambdaExpr, LambdaExprPartsKind)
+DEF_JOB(ConceptSpecializationExprVisit, ConceptSpecializationExpr,
+        ConceptSpecializationExprVisitKind)
+DEF_JOB(RequiresExprVisit, RequiresExpr, RequiresExprVisitKind)
 DEF_JOB(PostChildrenVisit, void, PostChildrenVisitKind)
 #undef DEF_JOB
 
@@ -2044,6 +2132,8 @@
   void VisitPseudoObjectExpr(const PseudoObjectExpr *E);
   void VisitOpaqueValueExpr(const OpaqueValueExpr *E);
   void VisitLambdaExpr(const LambdaExpr *E);
+  void VisitConceptSpecializationExpr(const ConceptSpecializationExpr *E);
+  void VisitRequiresExpr(const RequiresExpr *E);
   void VisitOMPExecutableDirective(const OMPExecutableDirective *D);
   void VisitOMPLoopBasedDirective(const OMPLoopBasedDirective *D);
   void VisitOMPLoopDirective(const OMPLoopDirective *D);
@@ -2887,6 +2977,15 @@
   AddStmt(E->getBody());
   WL.push_back(LambdaExprParts(E, Parent));
 }
+void EnqueueVisitor::VisitConceptSpecializationExpr(
+    const ConceptSpecializationExpr *E) {
+  WL.push_back(ConceptSpecializationExprVisit(E, Parent));
+}
+void EnqueueVisitor::VisitRequiresExpr(const RequiresExpr *E) {
+  WL.push_back(RequiresExprVisit(E, Parent));
+  for (ParmVarDecl *VD : E->getLocalParameters())
+    AddDecl(VD);
+}
 void EnqueueVisitor::VisitPseudoObjectExpr(const PseudoObjectExpr *E) {
   // Treat the expression like its syntactic form.
   Visit(E->getSyntacticForm());
@@ -3380,6 +3479,36 @@
       break;
     }
 
+    case VisitorJob::ConceptSpecializationExprVisitKind: {
+      const ConceptSpecializationExpr *E =
+          cast<ConceptSpecializationExprVisit>(&LI)->get();
+      if (NestedNameSpecifierLoc QualifierLoc =
+              E->getNestedNameSpecifierLoc()) {
+        if (VisitNestedNameSpecifierLoc(QualifierLoc))
+          return true;
+      }
+
+      if (E->getNamedConcept() &&
+          Visit(MakeCursorTemplateRef(E->getNamedConcept(),
+                                      E->getConceptNameLoc(), TU)))
+        return true;
+
+      if (auto Args = E->getTemplateArgsAsWritten()) {
+        for (const auto &Arg : Args->arguments()) {
+          if (VisitTemplateArgumentLoc(Arg))
+            return true;
+        }
+      }
+      break;
+    }
+
+    case VisitorJob::RequiresExprVisitKind: {
+      const RequiresExpr *E = cast<RequiresExprVisit>(&LI)->get();
+      for (const concepts::Requirement *R : E->getRequirements())
+        VisitConceptRequirement(*R);
+      break;
+    }
+
     case VisitorJob::PostChildrenVisitKind:
       if (PostChildrenVisitor(Parent, ClientData))
         return true;
@@ -5401,6 +5530,10 @@
     return cxstring::createRef("ObjCMessageExpr");
   case CXCursor_BuiltinBitCastExpr:
     return cxstring::createRef("BuiltinBitCastExpr");
+  case CXCursor_ConceptSpecializationExpr:
+    return cxstring::createRef("ConceptSpecializationExpr");
+  case CXCursor_RequiresExpr:
+    return cxstring::createRef("RequiresExpr");
   case CXCursor_UnexposedStmt:
     return cxstring::createRef("UnexposedStmt");
   case CXCursor_DeclStmt:
@@ -5751,6 +5884,8 @@
     return cxstring::createRef("attribute(warn_unused_result)");
   case CXCursor_AlignedAttr:
     return cxstring::createRef("attribute(aligned)");
+  case CXCursor_ConceptDecl:
+    return cxstring::createRef("ConceptDecl");
   }
 
   llvm_unreachable("Unhandled CXCursorKind");
diff --git a/clang/tools/libclang/CXCursor.cpp b/clang/tools/libclang/CXCursor.cpp
--- a/clang/tools/libclang/CXCursor.cpp
+++ b/clang/tools/libclang/CXCursor.cpp
@@ -299,8 +299,6 @@
   case Stmt::BinaryConditionalOperatorClass:
   case Stmt::TypeTraitExprClass:
   case Stmt::CoawaitExprClass:
-  case Stmt::ConceptSpecializationExprClass:
-  case Stmt::RequiresExprClass:
   case Stmt::DependentCoawaitExprClass:
   case Stmt::CoyieldExprClass:
   case Stmt::CXXBindTemporaryExprClass:
@@ -637,6 +635,14 @@
     return getSelectorIdentifierCursor(SelectorIdIndex, C);
   }
 
+  case Stmt::ConceptSpecializationExprClass:
+    K = CXCursor_ConceptSpecializationExpr;
+    break;
+
+  case Stmt::RequiresExprClass:
+    K = CXCursor_RequiresExpr;
+    break;
+
   case Stmt::MSDependentExistsStmtClass:
     K = CXCursor_UnexposedStmt;
     break;
diff --git a/clang/tools/libclang/CXIndexDataConsumer.h b/clang/tools/libclang/CXIndexDataConsumer.h
--- a/clang/tools/libclang/CXIndexDataConsumer.h
+++ b/clang/tools/libclang/CXIndexDataConsumer.h
@@ -409,6 +409,8 @@
   bool handleFunctionTemplate(const FunctionTemplateDecl *D);
   bool handleTypeAliasTemplate(const TypeAliasTemplateDecl *D);
 
+  bool handleConcept(const ConceptDecl *D);
+
   bool handleReference(const NamedDecl *D, SourceLocation Loc, CXCursor Cursor,
                        const NamedDecl *Parent,
                        const DeclContext *DC,
diff --git a/clang/tools/libclang/CXIndexDataConsumer.cpp b/clang/tools/libclang/CXIndexDataConsumer.cpp
--- a/clang/tools/libclang/CXIndexDataConsumer.cpp
+++ b/clang/tools/libclang/CXIndexDataConsumer.cpp
@@ -146,6 +146,11 @@
     DataConsumer.importedModule(D);
     return true;
   }
+
+  bool VisitConceptDecl(const ConceptDecl *D) {
+    DataConsumer.handleConcept(D);
+    return true;
+  }
 };
 
 CXSymbolRole getSymbolRole(SymbolRoleSet Role) {
@@ -883,6 +888,12 @@
   return handleDecl(D, D->getLocation(), getCursor(D), DInfo);
 }
 
+bool CXIndexDataConsumer::handleConcept(const ConceptDecl *D) {
+  DeclInfo DInfo(/*isRedeclaration=*/!D->isCanonicalDecl(),
+                 /*isDefinition=*/true, /*isContainer=*/false);
+  return handleDecl(D, D->getLocation(), getCursor(D), DInfo);
+}
+
 bool CXIndexDataConsumer::handleReference(const NamedDecl *D, SourceLocation Loc,
                                       CXCursor Cursor,
                                       const NamedDecl *Parent,
@@ -1249,7 +1260,6 @@
   case SymbolKind::TemplateTypeParm:
   case SymbolKind::TemplateTemplateParm:
   case SymbolKind::NonTypeTemplateParm:
-  case SymbolKind::Concept:
     return CXIdxEntity_Unexposed;
 
   case SymbolKind::Enum: return CXIdxEntity_Enum;
@@ -1289,6 +1299,8 @@
   case SymbolKind::Destructor: return CXIdxEntity_CXXDestructor;
   case SymbolKind::ConversionFunction: return CXIdxEntity_CXXConversionFunction;
   case SymbolKind::Parameter: return CXIdxEntity_Variable;
+  case SymbolKind::Concept:
+    return CXIdxEntity_CXXConcept;
   }
   llvm_unreachable("invalid symbol kind");
 }
diff --git a/clang/tools/libclang/CursorVisitor.h b/clang/tools/libclang/CursorVisitor.h
--- a/clang/tools/libclang/CursorVisitor.h
+++ b/clang/tools/libclang/CursorVisitor.h
@@ -19,6 +19,10 @@
 class PreprocessingRecord;
 class ASTUnit;
 
+namespace concepts {
+class Requirement;
+}
+
 namespace cxcursor {
 
 class VisitorJob {
@@ -37,6 +41,8 @@
     MemberRefVisitKind,
     SizeOfPackExprPartsKind,
     LambdaExprPartsKind,
+    ConceptSpecializationExprVisitKind,
+    RequiresExprVisitKind,
     PostChildrenVisitKind
   };
 
@@ -242,6 +248,9 @@
   bool VisitStaticAssertDecl(StaticAssertDecl *D);
   bool VisitFriendDecl(FriendDecl *D);
   bool VisitDecompositionDecl(DecompositionDecl *D);
+  bool VisitConceptDecl(ConceptDecl *D);
+  bool VisitTypeConstraint(const TypeConstraint &TC);
+  bool VisitConceptRequirement(const concepts::Requirement &R);
 
   // Name visitor
   bool VisitDeclarationNameInfo(DeclarationNameInfo Name);