diff --git a/clang/include/clang/ExtractAPI/API.h b/clang/include/clang/ExtractAPI/API.h
--- a/clang/include/clang/ExtractAPI/API.h
+++ b/clang/include/clang/ExtractAPI/API.h
@@ -69,6 +69,10 @@
     RK_StaticField,
     RK_CXXField,
     RK_CXXClass,
+    RK_ClassTemplate,
+    RK_ClassTemplateSpecialization,
+    RK_ClassTemplatePartialSpecialization,
+    RK_Concept,
     RK_CXXStaticMethod,
     RK_CXXInstanceMethod,
     RK_CXXConstructorMethod,
@@ -640,6 +644,75 @@
   virtual void anchor();
 };
 
+struct ClassTemplateRecord : CXXClassRecord {
+  Template Templ;
+
+  ClassTemplateRecord(StringRef USR, StringRef Name, PresumedLoc Loc,
+                      AvailabilitySet Availabilities, const DocComment &Comment,
+                      DeclarationFragments Declaration,
+                      DeclarationFragments SubHeading, Template Template,
+                      bool IsFromSystemHeader)
+      : CXXClassRecord(USR, Name, Loc, std::move(Availabilities), Comment,
+                       Declaration, SubHeading, RK_ClassTemplate,
+                       IsFromSystemHeader),
+        Templ(Template) {}
+
+  static bool classof(const APIRecord *Record) {
+    return Record->getKind() == RK_ClassTemplate;
+  }
+};
+
+struct ClassTemplateSpecRecord : CXXClassRecord {
+  ClassTemplateSpecRecord(StringRef USR, StringRef Name, PresumedLoc Loc,
+                          AvailabilitySet Availabilities,
+                          const DocComment &Comment,
+                          DeclarationFragments Declaration,
+                          DeclarationFragments SubHeading,
+                          bool IsFromSystemHeader)
+      : CXXClassRecord(USR, Name, Loc, std::move(Availabilities), Comment,
+                       Declaration, SubHeading, RK_ClassTemplateSpecialization,
+                       IsFromSystemHeader) {}
+
+  static bool classof(const APIRecord *Record) {
+    return Record->getKind() == RK_ClassTemplateSpecialization;
+  }
+};
+
+struct ClassTemplatePartialSpecRecord : CXXClassRecord {
+  Template Templ;
+  ClassTemplatePartialSpecRecord(StringRef USR, StringRef Name, PresumedLoc Loc,
+                                 AvailabilitySet Availabilities,
+                                 const DocComment &Comment,
+                                 DeclarationFragments Declaration,
+                                 DeclarationFragments SubHeading,
+                                 Template Template, bool IsFromSystemHeader)
+      : CXXClassRecord(USR, Name, Loc, std::move(Availabilities), Comment,
+                       Declaration, SubHeading, RK_ClassTemplateSpecialization,
+                       IsFromSystemHeader),
+        Templ(Template) {}
+
+  static bool classof(const APIRecord *Record) {
+    return Record->getKind() == RK_ClassTemplatePartialSpecialization;
+  }
+};
+
+struct ConceptRecord : APIRecord {
+  Template Templ;
+  ConceptRecord(StringRef USR, StringRef Name, PresumedLoc Loc,
+                AvailabilitySet Availabilities, const DocComment &Comment,
+                DeclarationFragments Declaration,
+                DeclarationFragments SubHeading, Template Template,
+                bool IsFromSystemHeader)
+      : APIRecord(RK_Concept, USR, Name, Loc, std::move(Availabilities),
+                  LinkageInfo::none(), Comment, Declaration, SubHeading,
+                  IsFromSystemHeader),
+        Templ(Template) {}
+
+  static bool classof(const APIRecord *Record) {
+    return Record->getKind() == RK_Concept;
+  }
+};
+
 /// This holds information associated with Objective-C categories.
 struct ObjCCategoryRecord : ObjCContainerRecord {
   SymbolReference Interface;
@@ -773,6 +846,12 @@
 template <> struct has_access<CXXMethodRecord> : public std::true_type {};
 template <> struct has_access<CXXFieldRecord> : public std::true_type {};
 
+template <typename RecordTy> struct has_template : public std::false_type {};
+template <> struct has_template<ClassTemplateRecord> : public std::true_type {};
+template <>
+struct has_template<ClassTemplatePartialSpecRecord> : public std::true_type {};
+template <> struct has_template<ConceptRecord> : public std::true_type {};
+
 /// APISet holds the set of API records collected from given inputs.
 class APISet {
 public:
@@ -870,6 +949,26 @@
               DeclarationFragments Declaration, DeclarationFragments SubHeading,
               APIRecord::RecordKind Kind, bool IsFromSystemHeader);
 
+  ClassTemplateRecord *
+  addClassTemplate(StringRef Name, StringRef USR, PresumedLoc Loc,
+                   AvailabilitySet Availability, const DocComment &Comment,
+                   DeclarationFragments Declaration,
+                   DeclarationFragments SubHeading, Template Template,
+                   bool IsFromSystemHeader);
+
+  ClassTemplateSpecRecord *
+  addClassTemplateSpec(StringRef Name, StringRef USR, PresumedLoc Loc,
+                       AvailabilitySet Availability, const DocComment &Comment,
+                       DeclarationFragments Declaration,
+                       DeclarationFragments SubHeading,
+                       bool IsFromSystemHeader);
+
+  ClassTemplatePartialSpecRecord *addClassTemplatePartialSpec(
+      StringRef Name, StringRef USR, PresumedLoc Loc,
+      AvailabilitySet Availability, const DocComment &Comment,
+      DeclarationFragments Declaration, DeclarationFragments SubHeading,
+      Template Template, bool IsFromSystemHeader);
+
   CXXMethodRecord *
   addCXXMethod(CXXClassRecord *CXXClassRecord, StringRef Name, StringRef USR,
                PresumedLoc Loc, AvailabilitySet Availability,
@@ -884,6 +983,13 @@
       FunctionSignature Signature, bool IsConstructor, AccessControl Access,
       bool IsFromSystemHeader);
 
+  ConceptRecord *addConcept(StringRef Name, StringRef USR, PresumedLoc Loc,
+                            AvailabilitySet Availability,
+                            const DocComment &Comment,
+                            DeclarationFragments Declaration,
+                            DeclarationFragments SubHeading, Template Template,
+                            bool IsFromSystemHeader);
+
   /// Create and add an Objective-C category record into the API set.
   ///
   /// Note: the caller is responsible for keeping the StringRef \p Name and
@@ -1012,6 +1118,19 @@
   const RecordMap<EnumRecord> &getEnums() const { return Enums; }
   const RecordMap<StructRecord> &getStructs() const { return Structs; }
   const RecordMap<CXXClassRecord> &getCXXClasses() const { return CXXClasses; }
+  const RecordMap<ConceptRecord> &getConcepts() const { return Concepts; }
+  const RecordMap<ClassTemplateRecord> &getClassTemplates() const {
+    return ClassTemplates;
+  }
+  const RecordMap<ClassTemplateSpecRecord> &
+  getClassTemplateSpecializations() const {
+    return ClassTemplateSpecializations;
+  }
+  const RecordMap<ClassTemplatePartialSpecRecord> &
+  getClassTemplatePartialSpecializations() const {
+    return ClassTemplatePartialSpecializations;
+  }
+  const RecordMap<ConceptRecord> &getRecords() const { return Concepts; }
   const RecordMap<ObjCCategoryRecord> &getObjCCategories() const {
     return ObjCCategories;
   }
@@ -1065,10 +1184,14 @@
   llvm::DenseMap<StringRef, APIRecord *> USRBasedLookupTable;
   RecordMap<GlobalFunctionRecord> GlobalFunctions;
   RecordMap<GlobalVariableRecord> GlobalVariables;
+  RecordMap<ConceptRecord> Concepts;
   RecordMap<StaticFieldRecord> StaticFields;
   RecordMap<EnumRecord> Enums;
   RecordMap<StructRecord> Structs;
   RecordMap<CXXClassRecord> CXXClasses;
+  RecordMap<ClassTemplateRecord> ClassTemplates;
+  RecordMap<ClassTemplateSpecRecord> ClassTemplateSpecializations;
+  RecordMap<ClassTemplatePartialSpecRecord> ClassTemplatePartialSpecializations;
   RecordMap<ObjCCategoryRecord> ObjCCategories;
   RecordMap<ObjCInterfaceRecord> ObjCInterfaces;
   RecordMap<ObjCProtocolRecord> ObjCProtocols;
diff --git a/clang/include/clang/ExtractAPI/DeclarationFragments.h b/clang/include/clang/ExtractAPI/DeclarationFragments.h
--- a/clang/include/clang/ExtractAPI/DeclarationFragments.h
+++ b/clang/include/clang/ExtractAPI/DeclarationFragments.h
@@ -22,6 +22,7 @@
 #include "clang/AST/Decl.h"
 #include "clang/AST/DeclCXX.h"
 #include "clang/AST/DeclObjC.h"
+#include "clang/AST/DeclTemplate.h"
 #include "clang/Lex/MacroInfo.h"
 #include "llvm/ADT/StringRef.h"
 #include <vector>
@@ -161,6 +162,11 @@
     return *this;
   }
 
+  DeclarationFragments &pop_back() {
+    Fragments.pop_back();
+    return *this;
+  }
+
   /// Append a text Fragment of a space character.
   ///
   /// \returns a reference to the DeclarationFragments object itself after
@@ -182,6 +188,50 @@
   std::vector<Fragment> Fragments;
 };
 
+class Template {
+  struct TemplateParameter {
+    // "class", "typename", or concept name
+    std::string Type;
+    std::string Name;
+    unsigned int Index;
+    unsigned int Depth;
+    bool IsParameterPack;
+
+    TemplateParameter(std::string Type, std::string Name, unsigned int Index,
+                      unsigned int Depth, bool IsParameterPack)
+        : Type(Type), Name(Name), Index(Index), Depth(Depth),
+          IsParameterPack(IsParameterPack) {}
+  };
+
+  struct TemplateConstraint {
+    // type name of the constraint, if it has one
+    std::string Type;
+    std::string Kind;
+    std::string LHS, RHS;
+  };
+  SmallVector<TemplateParameter> Parameters;
+  SmallVector<TemplateConstraint> Constraints;
+
+public:
+  Template() = default;
+
+  const SmallVector<TemplateParameter> &getParameters() const {
+    return Parameters;
+  }
+
+  const SmallVector<TemplateConstraint> &getConstraints() const {
+    return Constraints;
+  }
+
+  void addTemplateParameter(std::string Type, std::string Name,
+                            unsigned int Index, unsigned int Depth,
+                            bool IsParameterPack) {
+    Parameters.emplace_back(Type, Name, Index, Depth, IsParameterPack);
+  }
+
+  bool empty() const { return Parameters.empty() && Constraints.empty(); }
+};
+
 class AccessControl {
 public:
   AccessControl(std::string Access) : Access(Access) {}
@@ -259,6 +309,50 @@
     llvm_unreachable("Unhandled access control");
   }
 
+  /// Get template details from a template function, class, or variable
+  static Template getTemplate(const TemplateDecl *Decl) {
+    Template Template;
+    for (auto *const Parameter : *Decl->getTemplateParameters()) {
+      const auto *Param = dyn_cast<TemplateTypeParmDecl>(Parameter);
+      if (!Param) // some params are null
+        continue;
+      std::string Type;
+      if (Param->hasTypeConstraint())
+        Type = Param->getTypeConstraint()->getNamedConcept()->getName().str();
+      else if (Param->wasDeclaredWithTypename())
+        Type = "typename";
+      else
+        Type = "class";
+
+      Template.addTemplateParameter(Type, Param->getName().str(),
+                                    Param->getIndex(), Param->getDepth(),
+                                    Param->isParameterPack());
+    }
+    return Template;
+  }
+
+  static Template
+  getTemplate(const ClassTemplatePartialSpecializationDecl *Decl) {
+    Template Template;
+    for (auto *const Parameter : *Decl->getTemplateParameters()) {
+      const auto *Param = dyn_cast<TemplateTypeParmDecl>(Parameter);
+      if (!Param) // some params are null
+        continue;
+      std::string Type;
+      if (Param->hasTypeConstraint())
+        Type = Param->getTypeConstraint()->getNamedConcept()->getName().str();
+      else if (Param->wasDeclaredWithTypename())
+        Type = "typename";
+      else
+        Type = "class";
+
+      Template.addTemplateParameter(Type, Param->getName().str(),
+                                    Param->getIndex(), Param->getDepth(),
+                                    Param->isParameterPack());
+    }
+    return Template;
+  }
+
   /// Build DeclarationFragments for a variable declaration VarDecl.
   static DeclarationFragments getFragmentsForVar(const VarDecl *);
 
@@ -292,6 +386,28 @@
   static DeclarationFragments
   getFragmentsForOverloadedOperator(const CXXMethodDecl *);
 
+  static DeclarationFragments
+      getFragmentsForTemplateParameters(ArrayRef<NamedDecl *>);
+
+  static DeclarationFragments
+  getFragmentsForTemplateArgument(const ArrayRef<NamedDecl *>, std::string);
+
+  static DeclarationFragments
+  getFragmentsForTemplateArguments(const ArrayRef<TemplateArgument>,
+                                   ASTContext &,
+                                   const std::optional<ArrayRef<NamedDecl *>>);
+
+  static DeclarationFragments getFragmentsForConcept(const ConceptDecl *);
+
+  static DeclarationFragments
+  getFragmentsForRedeclarableTemplate(const RedeclarableTemplateDecl *);
+
+  static DeclarationFragments getFragmentsForClassTemplateSpecialization(
+      const ClassTemplateSpecializationDecl *);
+
+  static DeclarationFragments getFragmentsForClassTemplatePartialSpecialization(
+      const ClassTemplatePartialSpecializationDecl *);
+
   /// Build DeclarationFragments for an Objective-C category declaration
   /// ObjCCategoryDecl.
   static DeclarationFragments
diff --git a/clang/include/clang/ExtractAPI/ExtractAPIVisitor.h b/clang/include/clang/ExtractAPI/ExtractAPIVisitor.h
--- a/clang/include/clang/ExtractAPI/ExtractAPIVisitor.h
+++ b/clang/include/clang/ExtractAPI/ExtractAPIVisitor.h
@@ -15,6 +15,7 @@
 #define LLVM_CLANG_EXTRACTAPI_EXTRACT_API_VISITOR_H
 
 #include "clang/AST/DeclCXX.h"
+#include "clang/AST/DeclTemplate.h"
 #include "clang/Basic/OperatorKinds.h"
 #include "clang/Basic/Specifiers.h"
 #include "clang/ExtractAPI/DeclarationFragments.h"
@@ -52,10 +53,24 @@
 
   bool WalkUpFromCXXRecordDecl(const CXXRecordDecl *Decl);
 
+  bool WalkUpFromClassTemplateSpecializationDecl(
+      const ClassTemplateSpecializationDecl *Decl);
+
+  bool WalkUpFromClassTemplatePartialSpecializationDecl(
+      const ClassTemplatePartialSpecializationDecl *Decl);
+
   bool VisitRecordDecl(const RecordDecl *Decl);
 
   bool VisitCXXRecordDecl(const CXXRecordDecl *Decl);
 
+  bool VisitConceptDecl(const ConceptDecl *Decl);
+
+  bool VisitClassTemplateSpecializationDecl(
+      const ClassTemplateSpecializationDecl *Decl);
+
+  bool VisitClassTemplatePartialSpecializationDecl(
+      const ClassTemplatePartialSpecializationDecl *Decl);
+
   bool VisitObjCInterfaceDecl(const ObjCInterfaceDecl *Decl);
 
   bool VisitObjCProtocolDecl(const ObjCProtocolDecl *Decl);
@@ -328,6 +343,22 @@
   return true;
 }
 
+template <typename Derived>
+bool ExtractAPIVisitorBase<Derived>::WalkUpFromClassTemplateSpecializationDecl(
+    const ClassTemplateSpecializationDecl *Decl) {
+  getDerivedExtractAPIVisitor().VisitClassTemplateSpecializationDecl(Decl);
+  return true;
+}
+
+template <typename Derived>
+bool ExtractAPIVisitorBase<Derived>::
+    WalkUpFromClassTemplatePartialSpecializationDecl(
+        const ClassTemplatePartialSpecializationDecl *Decl) {
+  getDerivedExtractAPIVisitor().VisitClassTemplatePartialSpecializationDecl(
+      Decl);
+  return true;
+}
+
 template <typename Derived>
 bool ExtractAPIVisitorBase<Derived>::VisitRecordDecl(const RecordDecl *Decl) {
   if (!getDerivedExtractAPIVisitor().shouldDeclBeIncluded(Decl))
@@ -368,7 +399,8 @@
 template <typename Derived>
 bool ExtractAPIVisitorBase<Derived>::VisitCXXRecordDecl(
     const CXXRecordDecl *Decl) {
-  if (!getDerivedExtractAPIVisitor().shouldDeclBeIncluded(Decl))
+  if (!getDerivedExtractAPIVisitor().shouldDeclBeIncluded(Decl) ||
+      Decl->isImplicit())
     return true;
 
   StringRef Name = Decl->getName();
@@ -393,9 +425,23 @@
   else
     Kind = APIRecord::RecordKind::RK_CXXClass;
 
-  CXXClassRecord *CXXClassRecord =
-      API.addCXXClass(Name, USR, Loc, AvailabilitySet(Decl), Comment,
-                      Declaration, SubHeading, Kind, isInSystemHeader(Decl));
+  CXXClassRecord *CXXClassRecord;
+  if (Decl->getDescribedClassTemplate()) {
+    // Inject template fragments before class fragments.
+    Declaration.insert(
+        Declaration.begin(),
+        DeclarationFragmentsBuilder::getFragmentsForRedeclarableTemplate(
+            Decl->getDescribedClassTemplate()));
+    // Cast to easily use previous declaration to get bases.
+    CXXClassRecord = API.addClassTemplate(
+        Name, USR, Loc, AvailabilitySet(Decl), Comment, Declaration, SubHeading,
+        DeclarationFragmentsBuilder::getTemplate(
+            Decl->getDescribedClassTemplate()),
+        isInSystemHeader(Decl));
+  } else
+    CXXClassRecord =
+        API.addCXXClass(Name, USR, Loc, AvailabilitySet(Decl), Comment,
+                        Declaration, SubHeading, Kind, isInSystemHeader(Decl));
 
   // FIXME: store AccessSpecifier given by inheritance
   for (const auto BaseSpecifier : Decl->bases()) {
@@ -416,6 +462,116 @@
   return true;
 }
 
+template <typename Derived>
+bool ExtractAPIVisitorBase<Derived>::VisitConceptDecl(const ConceptDecl *Decl) {
+  if (!getDerivedExtractAPIVisitor().shouldDeclBeIncluded(Decl))
+    return true;
+
+  StringRef Name = Decl->getName();
+  StringRef USR = API.recordUSR(Decl);
+  PresumedLoc Loc =
+      Context.getSourceManager().getPresumedLoc(Decl->getLocation());
+  DocComment Comment;
+  if (auto *RawComment =
+          getDerivedExtractAPIVisitor().fetchRawCommentForDecl(Decl))
+    Comment = RawComment->getFormattedLines(Context.getSourceManager(),
+                                            Context.getDiagnostics());
+  DeclarationFragments Declaration =
+      DeclarationFragmentsBuilder::getFragmentsForConcept(Decl);
+  DeclarationFragments SubHeading =
+      DeclarationFragmentsBuilder::getSubHeading(Decl);
+  API.addConcept(Name, USR, Loc, AvailabilitySet(Decl), Comment, Declaration,
+                 SubHeading, DeclarationFragmentsBuilder::getTemplate(Decl),
+                 isInSystemHeader(Decl));
+  return true;
+}
+
+template <typename Derived>
+bool ExtractAPIVisitorBase<Derived>::VisitClassTemplateSpecializationDecl(
+    const ClassTemplateSpecializationDecl *Decl) {
+  if (!getDerivedExtractAPIVisitor().shouldDeclBeIncluded(Decl))
+    return true;
+
+  StringRef Name = Decl->getName();
+  StringRef USR = API.recordUSR(Decl);
+  PresumedLoc Loc =
+      Context.getSourceManager().getPresumedLoc(Decl->getLocation());
+  DocComment Comment;
+  if (auto *RawComment =
+          getDerivedExtractAPIVisitor().fetchRawCommentForDecl(Decl))
+    Comment = RawComment->getFormattedLines(Context.getSourceManager(),
+                                            Context.getDiagnostics());
+  DeclarationFragments Declaration =
+      DeclarationFragmentsBuilder::getFragmentsForClassTemplateSpecialization(
+          Decl);
+  DeclarationFragments SubHeading =
+      DeclarationFragmentsBuilder::getSubHeading(Decl);
+
+  ClassTemplateSpecRecord *ClassTemplateSpecializationRecord =
+      API.addClassTemplateSpec(Name, USR, Loc, AvailabilitySet(Decl), Comment,
+                               Declaration, SubHeading, isInSystemHeader(Decl));
+
+  // FIXME: store AccessSpecifier given by inheritance
+  for (const auto BaseSpecifier : Decl->bases()) {
+    SymbolReference BaseClass;
+    CXXRecordDecl *BaseClassDecl =
+        BaseSpecifier.getType().getTypePtr()->getAsCXXRecordDecl();
+    BaseClass.Name = BaseClassDecl->getName();
+    BaseClass.USR = API.recordUSR(BaseClassDecl);
+    ClassTemplateSpecializationRecord->Bases.emplace_back(BaseClass);
+  }
+
+  getDerivedExtractAPIVisitor().recordCXXFields(
+      ClassTemplateSpecializationRecord, Decl->fields());
+  getDerivedExtractAPIVisitor().recordCXXMethods(
+      ClassTemplateSpecializationRecord, Decl->methods());
+  return true;
+}
+
+template <typename Derived>
+bool ExtractAPIVisitorBase<Derived>::
+    VisitClassTemplatePartialSpecializationDecl(
+        const ClassTemplatePartialSpecializationDecl *Decl) {
+  if (!getDerivedExtractAPIVisitor().shouldDeclBeIncluded(Decl))
+    return true;
+
+  StringRef Name = Decl->getName();
+  StringRef USR = API.recordUSR(Decl);
+  PresumedLoc Loc =
+      Context.getSourceManager().getPresumedLoc(Decl->getLocation());
+  DocComment Comment;
+  if (auto *RawComment =
+          getDerivedExtractAPIVisitor().fetchRawCommentForDecl(Decl))
+    Comment = RawComment->getFormattedLines(Context.getSourceManager(),
+                                            Context.getDiagnostics());
+  DeclarationFragments Declaration = DeclarationFragmentsBuilder::
+      getFragmentsForClassTemplatePartialSpecialization(Decl);
+  DeclarationFragments SubHeading =
+      DeclarationFragmentsBuilder::getSubHeading(Decl);
+
+  ClassTemplatePartialSpecRecord *ClassTemplatePartialSpecRecord =
+      API.addClassTemplatePartialSpec(
+          Name, USR, Loc, AvailabilitySet(Decl), Comment, Declaration,
+          SubHeading, DeclarationFragmentsBuilder::getTemplate(Decl),
+          isInSystemHeader(Decl));
+
+  // FIXME: store AccessSpecifier given by inheritance
+  for (const auto BaseSpecifier : Decl->bases()) {
+    SymbolReference BaseClass;
+    CXXRecordDecl *BaseClassDecl =
+        BaseSpecifier.getType().getTypePtr()->getAsCXXRecordDecl();
+    BaseClass.Name = BaseClassDecl->getName();
+    BaseClass.USR = API.recordUSR(BaseClassDecl);
+    ClassTemplatePartialSpecRecord->Bases.emplace_back(BaseClass);
+  }
+
+  getDerivedExtractAPIVisitor().recordCXXFields(ClassTemplatePartialSpecRecord,
+                                                Decl->fields());
+  getDerivedExtractAPIVisitor().recordCXXMethods(ClassTemplatePartialSpecRecord,
+                                                 Decl->methods());
+  return true;
+}
+
 template <typename Derived>
 bool ExtractAPIVisitorBase<Derived>::VisitObjCInterfaceDecl(
     const ObjCInterfaceDecl *Decl) {
diff --git a/clang/include/clang/ExtractAPI/Serialization/SerializerBase.h b/clang/include/clang/ExtractAPI/Serialization/SerializerBase.h
--- a/clang/include/clang/ExtractAPI/Serialization/SerializerBase.h
+++ b/clang/include/clang/ExtractAPI/Serialization/SerializerBase.h
@@ -33,6 +33,14 @@
 
     getDerived()->traverseCXXClassRecords();
 
+    getDerived()->traverseClassTemplateRecords();
+
+    getDerived()->traverseClassTemplateSpecRecords();
+
+    getDerived()->traverseClassTemplatePartialSpecRecords();
+
+    getDerived()->traverseConcepts();
+
     getDerived()->traverseStructRecords();
 
     getDerived()->traverseObjCInterfaces();
@@ -74,6 +82,28 @@
       getDerived()->visitCXXClassRecord(*Class.second);
   }
 
+  void traverseClassTemplateRecords() {
+    for (const auto &ClassTemplate : API.getClassTemplates())
+      getDerived()->visitClassTemplateRecord(*ClassTemplate.second);
+  }
+
+  void traverseClassTemplateSpecRecords() {
+    for (const auto &ClassTemplateSpec : API.getClassTemplateSpecializations())
+      getDerived()->visitClassTemplateSpecRecord(*ClassTemplateSpec.second);
+  }
+
+  void traverseClassTemplatePartialSpecRecords() {
+    for (const auto &ClassTemplatePartialSpec :
+         API.getClassTemplatePartialSpecializations())
+      getDerived()->visitClassTemplatePartialSpecRecord(
+          *ClassTemplatePartialSpec.second);
+  }
+
+  void traverseConcepts() {
+    for (const auto &Concept : API.getConcepts())
+      getDerived()->visitConceptRecord(*Concept.second);
+  }
+
   void traverseObjCInterfaces() {
     for (const auto &Interface : API.getObjCInterfaces())
       getDerived()->visitObjCContainerRecord(*Interface.second);
@@ -110,6 +140,13 @@
 
   void visitCXXClassRecord(const CXXClassRecord &Record){};
 
+  void visitClassTemplateRecord(const ClassTemplateRecord &Record){};
+
+  void visitClassTemplateSpecRecord(const ClassTemplateSpecRecord &Record);
+
+  void visitClassTemplatePartialSpecRecord(
+      const ClassTemplatePartialSpecRecord &Record);
+
   /// Visit an Objective-C container record.
   void visitObjCContainerRecord(const ObjCContainerRecord &Record){};
 
diff --git a/clang/include/clang/ExtractAPI/Serialization/SymbolGraphSerializer.h b/clang/include/clang/ExtractAPI/Serialization/SymbolGraphSerializer.h
--- a/clang/include/clang/ExtractAPI/Serialization/SymbolGraphSerializer.h
+++ b/clang/include/clang/ExtractAPI/Serialization/SymbolGraphSerializer.h
@@ -92,6 +92,10 @@
   /// Get the string representation of the relationship kind.
   static StringRef getRelationshipString(RelationshipKind Kind);
 
+  enum ConstraintKind { Conformance, ConditionalConformance };
+
+  static StringRef getConstraintString(ConstraintKind Kind);
+
 private:
   /// Just serialize the currently recorded objects in Symbol Graph format.
   Object serializeCurrentGraph();
@@ -164,6 +168,15 @@
 
   void visitCXXClassRecord(const CXXClassRecord &Record);
 
+  void visitClassTemplateRecord(const ClassTemplateRecord &Record);
+
+  void visitClassTemplateSpecRecord(const ClassTemplateSpecRecord &Record);
+
+  void visitClassTemplatePartialSpecRecord(
+      const ClassTemplatePartialSpecRecord &Record);
+
+  void visitConceptRecord(const ConceptRecord &Record);
+
   /// Visit an Objective-C container record.
   void visitObjCContainerRecord(const ObjCContainerRecord &Record);
 
diff --git a/clang/lib/ExtractAPI/API.cpp b/clang/lib/ExtractAPI/API.cpp
--- a/clang/lib/ExtractAPI/API.cpp
+++ b/clang/lib/ExtractAPI/API.cpp
@@ -159,6 +159,49 @@
                            SubHeading, Kind, IsFromSystemHeader);
 }
 
+ClassTemplateRecord *APISet::addClassTemplate(
+    StringRef Name, StringRef USR, PresumedLoc Loc,
+    AvailabilitySet Availability, const DocComment &Comment,
+    DeclarationFragments Declaration, DeclarationFragments SubHeading,
+    Template Template, bool IsFromSystemHeader) {
+
+  return addTopLevelRecord(USRBasedLookupTable, ClassTemplates, USR, Name, Loc,
+                           std::move(Availability), Comment, Declaration,
+                           SubHeading, Template, IsFromSystemHeader);
+}
+
+ClassTemplateSpecRecord *APISet::addClassTemplateSpec(
+    StringRef Name, StringRef USR, PresumedLoc Loc,
+    AvailabilitySet Availability, const DocComment &Comment,
+    DeclarationFragments Declaration, DeclarationFragments SubHeading,
+    bool IsFromSystemHeader) {
+  return addTopLevelRecord(USRBasedLookupTable, ClassTemplateSpecializations,
+                           USR, Name, Loc, std::move(Availability), Comment,
+                           Declaration, SubHeading, IsFromSystemHeader);
+}
+
+ClassTemplatePartialSpecRecord *APISet::addClassTemplatePartialSpec(
+    StringRef Name, StringRef USR, PresumedLoc Loc,
+    AvailabilitySet Availability, const DocComment &Comment,
+    DeclarationFragments Declaration, DeclarationFragments SubHeading,
+    Template Template, bool IsFromSystemHeader) {
+  return addTopLevelRecord(USRBasedLookupTable,
+                           ClassTemplatePartialSpecializations, USR, Name, Loc,
+                           std::move(Availability), Comment, Declaration,
+                           SubHeading, Template, IsFromSystemHeader);
+}
+
+ConceptRecord *APISet::addConcept(StringRef Name, StringRef USR,
+                                  PresumedLoc Loc, AvailabilitySet Availability,
+                                  const DocComment &Comment,
+                                  DeclarationFragments Declaration,
+                                  DeclarationFragments SubHeading,
+                                  Template Template, bool IsFromSystemHeader) {
+  return addTopLevelRecord(USRBasedLookupTable, Concepts, USR, Name, Loc,
+                           std::move(Availability), Comment, Declaration,
+                           SubHeading, Template, IsFromSystemHeader);
+}
+
 CXXMethodRecord *APISet::addCXXMethod(
     CXXClassRecord *CXXClassRecord, StringRef Name, StringRef USR,
     PresumedLoc Loc, AvailabilitySet Availability, const DocComment &Comment,
diff --git a/clang/lib/ExtractAPI/DeclarationFragments.cpp b/clang/lib/ExtractAPI/DeclarationFragments.cpp
--- a/clang/lib/ExtractAPI/DeclarationFragments.cpp
+++ b/clang/lib/ExtractAPI/DeclarationFragments.cpp
@@ -735,6 +735,175 @@
   return Fragments.append(";", DeclarationFragments::FragmentKind::Text);
 }
 
+// Get fragments for template parameters, e.g. T in tempalte<typename T> ...
+DeclarationFragments
+DeclarationFragmentsBuilder::getFragmentsForTemplateParameters(
+    ArrayRef<NamedDecl *> ParameterArray) {
+  DeclarationFragments Fragments;
+  for (unsigned i = 0, end = ParameterArray.size(); i != end; ++i) {
+    if (i)
+      Fragments.append(",", DeclarationFragments::FragmentKind::Text)
+          .appendSpace();
+
+    const auto *TemplateParam =
+        dyn_cast<TemplateTypeParmDecl>(ParameterArray[i]);
+    if (!TemplateParam)
+      continue;
+    if (TemplateParam->hasTypeConstraint())
+      Fragments.append(TemplateParam->getTypeConstraint()
+                           ->getNamedConcept()
+                           ->getName()
+                           .str(),
+                       DeclarationFragments::FragmentKind::TypeIdentifier);
+    else if (TemplateParam->wasDeclaredWithTypename())
+      Fragments.append("typename", DeclarationFragments::FragmentKind::Keyword);
+    else
+      Fragments.append("class", DeclarationFragments::FragmentKind::Keyword);
+
+    if (TemplateParam->isParameterPack())
+      Fragments.append("...", DeclarationFragments::FragmentKind::Text);
+
+    Fragments.appendSpace().append(
+        TemplateParam->getName(),
+        DeclarationFragments::FragmentKind::GenericParameter);
+  }
+  return Fragments;
+}
+
+// Get a name Fragment by finding the matching template parameter for an arg
+DeclarationFragments
+DeclarationFragmentsBuilder::getFragmentsForTemplateArgument(
+    const ArrayRef<NamedDecl *> TemplateParameters, std::string TypeParameter) {
+  DeclarationFragments Fragments;
+  // The arg is a generic parameter from a partial spec, e.g. T in
+  // template<typename T> Foo<T, int>. Those names appear as
+  // "type-parameter-<index>-<depth>", so we must find its name from the
+  // template's parameter list.
+  for (unsigned j = 0; j < TemplateParameters.size(); ++j) {
+    const auto *Parameter =
+        dyn_cast<TemplateTypeParmDecl>(TemplateParameters[j]);
+    if (TypeParameter.compare("type-parameter-" +
+                              std::to_string(Parameter->getIndex()) + "-" +
+                              std::to_string(Parameter->getDepth())) == 0) {
+      return Fragments.append(
+          TemplateParameters[j]->getName(),
+          DeclarationFragments::FragmentKind::GenericParameter);
+    }
+  }
+  return Fragments;
+}
+
+// Get fragments for template arguments, e.g. int in template<typename T>
+// Foo<int>;
+//
+// Note: TemplateParameters is only necessary if the Decl is a
+// PartialSpecialization, where we need the parameters to deduce the name of the
+// argument.
+DeclarationFragments
+DeclarationFragmentsBuilder::getFragmentsForTemplateArguments(
+    const ArrayRef<TemplateArgument> TemplateArguments, ASTContext &Context,
+    const std::optional<ArrayRef<NamedDecl *>> TemplateParameters) {
+  DeclarationFragments Fragments;
+  for (unsigned i = 0, end = TemplateArguments.size(); i != end; ++i) {
+    if (i)
+      Fragments.append(",", DeclarationFragments::FragmentKind::Text)
+          .appendSpace();
+
+    std::string Type = TemplateArguments[i].getAsType().getAsString();
+    DeclarationFragments After;
+    if (Type.substr(0, 14).compare("type-parameter") == 0) {
+      Fragments.append(
+          getFragmentsForTemplateArgument(*TemplateParameters, Type));
+    } else
+      // A non-generic arg
+      Fragments.append(getFragmentsForType(TemplateArguments[i].getAsType(),
+                                           Context, After));
+
+    if (TemplateArguments[i].isPackExpansion())
+      Fragments.append("...", DeclarationFragments::FragmentKind::Text);
+  }
+  return Fragments;
+}
+
+DeclarationFragments DeclarationFragmentsBuilder::getFragmentsForConcept(
+    const ConceptDecl *Concept) {
+  DeclarationFragments Fragments;
+  return Fragments
+      .append("template", DeclarationFragments::FragmentKind::Keyword)
+      .append("<", DeclarationFragments::FragmentKind::Text)
+      .append(getFragmentsForTemplateParameters(
+          Concept->getTemplateParameters()->asArray()))
+      .append("> ", DeclarationFragments::FragmentKind::Text)
+      .append("concept", DeclarationFragments::FragmentKind::Keyword)
+      .appendSpace()
+      .append(Concept->getName().str(),
+              DeclarationFragments::FragmentKind::Identifier)
+      .append(";", DeclarationFragments::FragmentKind::Text);
+}
+
+DeclarationFragments
+DeclarationFragmentsBuilder::getFragmentsForRedeclarableTemplate(
+    const RedeclarableTemplateDecl *RedeclarableTemplate) {
+  DeclarationFragments Fragments;
+  Fragments.append("template", DeclarationFragments::FragmentKind::Keyword)
+      .append("<", DeclarationFragments::FragmentKind::Text)
+      .append(getFragmentsForTemplateParameters(
+          RedeclarableTemplate->getTemplateParameters()->asArray()))
+      .append(">", DeclarationFragments::FragmentKind::Text)
+      .appendSpace();
+
+  if (isa<TypeAliasTemplateDecl>(RedeclarableTemplate))
+    Fragments.appendSpace()
+        .append("using", DeclarationFragments::FragmentKind::Keyword)
+        .appendSpace()
+        .append(RedeclarableTemplate->getName(),
+                DeclarationFragments::FragmentKind::Identifier);
+  // the templated records will be resposbible for injecting their templates
+  return Fragments.appendSpace();
+}
+
+DeclarationFragments
+DeclarationFragmentsBuilder::getFragmentsForClassTemplateSpecialization(
+    const ClassTemplateSpecializationDecl *Decl) {
+  DeclarationFragments Fragments;
+  return Fragments
+      .append("template", DeclarationFragments::FragmentKind::Keyword)
+      .append("<", DeclarationFragments::FragmentKind::Text)
+      .append(">", DeclarationFragments::FragmentKind::Text)
+      .appendSpace()
+      .append(DeclarationFragmentsBuilder::getFragmentsForCXXClass(
+          cast<CXXRecordDecl>(Decl)))
+      .pop_back() // there is an extra semicolon now
+      .append("<", DeclarationFragments::FragmentKind::Text)
+      .append(
+          getFragmentsForTemplateArguments(Decl->getTemplateArgs().asArray(),
+                                           Decl->getASTContext(), std::nullopt))
+      .append(">", DeclarationFragments::FragmentKind::Text)
+      .append(";", DeclarationFragments::FragmentKind::Text);
+}
+
+DeclarationFragments
+DeclarationFragmentsBuilder::getFragmentsForClassTemplatePartialSpecialization(
+    const ClassTemplatePartialSpecializationDecl *Decl) {
+  DeclarationFragments Fragments;
+  return Fragments
+      .append("template", DeclarationFragments::FragmentKind::Keyword)
+      .append("<", DeclarationFragments::FragmentKind::Text)
+      .append(getFragmentsForTemplateParameters(
+          Decl->getTemplateParameters()->asArray()))
+      .append(">", DeclarationFragments::FragmentKind::Text)
+      .appendSpace()
+      .append(DeclarationFragmentsBuilder::getFragmentsForCXXClass(
+          cast<CXXRecordDecl>(Decl)))
+      .pop_back() // there is an extra semicolon now
+      .append("<", DeclarationFragments::FragmentKind::Text)
+      .append(getFragmentsForTemplateArguments(
+          Decl->getTemplateArgs().asArray(), Decl->getASTContext(),
+          Decl->getTemplateParameters()->asArray()))
+      .append(">", DeclarationFragments::FragmentKind::Text)
+      .append(";", DeclarationFragments::FragmentKind::Text);
+}
+
 DeclarationFragments
 DeclarationFragmentsBuilder::getFragmentsForMacro(StringRef Name,
                                                   const MacroDirective *MD) {
diff --git a/clang/lib/ExtractAPI/Serialization/SymbolGraphSerializer.cpp b/clang/lib/ExtractAPI/Serialization/SymbolGraphSerializer.cpp
--- a/clang/lib/ExtractAPI/Serialization/SymbolGraphSerializer.cpp
+++ b/clang/lib/ExtractAPI/Serialization/SymbolGraphSerializer.cpp
@@ -387,10 +387,17 @@
     Kind["identifier"] = AddLangPrefix("type.property");
     Kind["displayName"] = "Type Property";
     break;
+  case APIRecord::RK_ClassTemplate:
+  case APIRecord::RK_ClassTemplateSpecialization:
+  case APIRecord::RK_ClassTemplatePartialSpecialization:
   case APIRecord::RK_CXXClass:
     Kind["identifier"] = AddLangPrefix("class");
     Kind["displayName"] = "Class";
     break;
+  case APIRecord::RK_Concept:
+    Kind["identifier"] = AddLangPrefix("concept");
+    Kind["displayName"] = "Concept";
+    break;
   case APIRecord::RK_CXXStaticMethod:
     Kind["identifier"] = AddLangPrefix("type.method");
     Kind["displayName"] = "Static Method";
@@ -536,6 +543,52 @@
   serializeString(Paren, "accessLevel", accessLevel);
 }
 
+template <typename RecordTy>
+std::optional<Object> serializeTemplateMixinImpl(const RecordTy &Record,
+                                                 std::true_type) {
+  const auto &Template = Record.Templ;
+  if (Template.empty())
+    return std::nullopt;
+
+  Object Generics;
+  Array GenericParameters;
+  for (const auto Param : Template.getParameters()) {
+    Object Parameter;
+    Parameter["name"] = Param.Name;
+    Parameter["index"] = Param.Index;
+    Parameter["depth"] = Param.Depth;
+    GenericParameters.emplace_back(std::move(Parameter));
+  }
+  if (!GenericParameters.empty())
+    Generics["parameters"] = std::move(GenericParameters);
+
+  Array GenericConstraints;
+  for (const auto Constr : Template.getConstraints()) {
+    Object Constraint;
+    Constraint["kind"] = Constr.Kind;
+    Constraint["lhs"] = Constr.LHS;
+    Constraint["rhs"] = Constr.RHS;
+    GenericConstraints.emplace_back(std::move(Constraint));
+  }
+
+  if (!GenericConstraints.empty())
+    Generics["constraints"] = std::move(GenericConstraints);
+
+  return Generics;
+}
+
+template <typename RecordTy>
+std::optional<Object> serializeTemplateMixinImpl(const RecordTy &Record,
+                                                 std::false_type) {
+  return std::nullopt;
+}
+
+template <typename RecordTy>
+void serializeTemplateMixin(Object &Paren, const RecordTy &Record) {
+  serializeObject(Paren, "swiftGenerics",
+                  serializeTemplateMixinImpl(Record, has_template<RecordTy>()));
+}
+
 struct PathComponent {
   StringRef USR;
   StringRef Name;
@@ -680,6 +733,7 @@
 
   serializeFunctionSignatureMixin(Obj, Record);
   serializeAccessMixin(Obj, Record);
+  serializeTemplateMixin(Obj, Record);
 
   return Obj;
 }
@@ -713,6 +767,16 @@
   llvm_unreachable("Unhandled relationship kind");
 }
 
+StringRef SymbolGraphSerializer::getConstraintString(ConstraintKind Kind) {
+  switch (Kind) {
+  case ConstraintKind::Conformance:
+    return "conformance";
+  case ConstraintKind::ConditionalConformance:
+    return "conditionalConformance";
+  }
+  llvm_unreachable("Unhandled constraint kind");
+}
+
 void SymbolGraphSerializer::serializeRelationship(RelationshipKind Kind,
                                                   SymbolReference Source,
                                                   SymbolReference Target) {
@@ -783,6 +847,56 @@
     serializeRelationship(RelationshipKind::InheritsFrom, Record, Base);
 }
 
+void SymbolGraphSerializer::visitClassTemplateRecord(
+    const ClassTemplateRecord &Record) {
+  auto Class = serializeAPIRecord(Record);
+  if (!Class)
+    return;
+
+  Symbols.emplace_back(std::move(*Class));
+  serializeMembers(Record, Record.Fields);
+  serializeMembers(Record, Record.Methods);
+
+  for (const auto Base : Record.Bases)
+    serializeRelationship(RelationshipKind::InheritsFrom, Record, Base);
+}
+
+void SymbolGraphSerializer::visitClassTemplateSpecRecord(
+    const ClassTemplateSpecRecord &Record) {
+  auto Class = serializeAPIRecord(Record);
+  if (!Class)
+    return;
+
+  Symbols.emplace_back(std::move(*Class));
+  serializeMembers(Record, Record.Fields);
+  serializeMembers(Record, Record.Methods);
+
+  for (const auto Base : Record.Bases)
+    serializeRelationship(RelationshipKind::InheritsFrom, Record, Base);
+}
+
+void SymbolGraphSerializer::visitClassTemplatePartialSpecRecord(
+    const ClassTemplatePartialSpecRecord &Record) {
+  auto Class = serializeAPIRecord(Record);
+  if (!Class)
+    return;
+
+  Symbols.emplace_back(std::move(*Class));
+  serializeMembers(Record, Record.Fields);
+  serializeMembers(Record, Record.Methods);
+
+  for (const auto Base : Record.Bases)
+    serializeRelationship(RelationshipKind::InheritsFrom, Record, Base);
+}
+
+void SymbolGraphSerializer::visitConceptRecord(const ConceptRecord &Record) {
+  auto Concept = serializeAPIRecord(Record);
+  if (!Concept)
+    return;
+
+  Symbols.emplace_back(std::move(*Concept));
+}
+
 void SymbolGraphSerializer::visitObjCContainerRecord(
     const ObjCContainerRecord &Record) {
   auto ObjCContainer = serializeAPIRecord(Record);
diff --git a/clang/test/ExtractAPI/class_template.cpp b/clang/test/ExtractAPI/class_template.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/ExtractAPI/class_template.cpp
@@ -0,0 +1,133 @@
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+// RUN: sed -e "s@INPUT_DIR@%{/t:regex_replacement}@g" \
+// RUN: %t/reference.output.json.in >> %t/reference.output.json
+// RUN: %clang_cc1 -extract-api -triple arm64-apple-macosx \
+// RUN:   -x c++-header %t/input.h -o %t/output.json -verify
+
+// Generator version is not consistent across test runs, normalize it.
+// RUN: sed -e "s@\"generator\": \".*\"@\"generator\": \"?\"@g" \
+// RUN: %t/output.json >> %t/output-normalized.json
+// RUN: diff %t/reference.output.json %t/output-normalized.json
+
+//--- input.h
+template<typename T> class Foo {};
+
+/// expected-no-diagnostics
+
+//--- reference.output.json.in
+{
+  "metadata": {
+    "formatVersion": {
+      "major": 0,
+      "minor": 5,
+      "patch": 3
+    },
+    "generator": "?"
+  },
+  "module": {
+    "name": "",
+    "platform": {
+      "architecture": "arm64",
+      "operatingSystem": {
+        "minimumVersion": {
+          "major": 11,
+          "minor": 0,
+          "patch": 0
+        },
+        "name": "macosx"
+      },
+      "vendor": "apple"
+    }
+  },
+  "relationships": [],
+  "symbols": [
+    {
+      "accessLevel": "public",
+      "declarationFragments": [
+        {
+          "kind": "keyword",
+          "spelling": "template"
+        },
+        {
+          "kind": "text",
+          "spelling": "<"
+        },
+        {
+          "kind": "keyword",
+          "spelling": "typename"
+        },
+        {
+          "kind": "text",
+          "spelling": " "
+        },
+        {
+          "kind": "genericParameter",
+          "spelling": "T"
+        },
+        {
+          "kind": "text",
+          "spelling": "> "
+        },
+        {
+          "kind": "keyword",
+          "spelling": "class"
+        },
+        {
+          "kind": "text",
+          "spelling": " "
+        },
+        {
+          "kind": "identifier",
+          "spelling": "Foo"
+        },
+        {
+          "kind": "text",
+          "spelling": ";"
+        }
+      ],
+      "identifier": {
+        "interfaceLanguage": "c++",
+        "precise": "c:@ST>1#T@Foo"
+      },
+      "kind": {
+        "displayName": "Class",
+        "identifier": "c++.class"
+      },
+      "location": {
+        "position": {
+          "character": 28,
+          "line": 1
+        },
+        "uri": "file://INPUT_DIR/input.h"
+      },
+      "names": {
+        "navigator": [
+          {
+            "kind": "identifier",
+            "spelling": "Foo"
+          }
+        ],
+        "subHeading": [
+          {
+            "kind": "identifier",
+            "spelling": "Foo"
+          }
+        ],
+        "title": "Foo"
+      },
+      "pathComponents": [
+        "Foo"
+      ],
+      "swiftGenerics": {
+        "parameters": [
+          {
+            "depth": 0,
+            "index": 0,
+            "name": "T"
+          }
+        ]
+      }
+    }
+  ]
+}
diff --git a/clang/test/ExtractAPI/class_template_partial_spec.cpp b/clang/test/ExtractAPI/class_template_partial_spec.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/ExtractAPI/class_template_partial_spec.cpp
@@ -0,0 +1,260 @@
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+// RUN: sed -e "s@INPUT_DIR@%{/t:regex_replacement}@g" \
+// RUN: %t/reference.output.json.in >> %t/reference.output.json
+// RUN: %clang_cc1 -extract-api -triple arm64-apple-macosx \
+// RUN:   -x c++-header %t/input.h -o %t/output.json -verify
+
+// Generator version is not consistent across test runs, normalize it.
+// RUN: sed -e "s@\"generator\": \".*\"@\"generator\": \"?\"@g" \
+// RUN: %t/output.json >> %t/output-normalized.json
+// RUN: diff %t/reference.output.json %t/output-normalized.json
+
+//--- input.h
+template<typename X, typename Y> class Foo {};
+
+template<typename Z> class Foo<Z, int> {};
+
+/// expected-no-diagnostics
+
+//--- reference.output.json.in
+{
+  "metadata": {
+    "formatVersion": {
+      "major": 0,
+      "minor": 5,
+      "patch": 3
+    },
+    "generator": "?"
+  },
+  "module": {
+    "name": "",
+    "platform": {
+      "architecture": "arm64",
+      "operatingSystem": {
+        "minimumVersion": {
+          "major": 11,
+          "minor": 0,
+          "patch": 0
+        },
+        "name": "macosx"
+      },
+      "vendor": "apple"
+    }
+  },
+  "relationships": [],
+  "symbols": [
+    {
+      "accessLevel": "public",
+      "declarationFragments": [
+        {
+          "kind": "keyword",
+          "spelling": "template"
+        },
+        {
+          "kind": "text",
+          "spelling": "<"
+        },
+        {
+          "kind": "keyword",
+          "spelling": "typename"
+        },
+        {
+          "kind": "text",
+          "spelling": " "
+        },
+        {
+          "kind": "genericParameter",
+          "spelling": "X"
+        },
+        {
+          "kind": "text",
+          "spelling": ", "
+        },
+        {
+          "kind": "keyword",
+          "spelling": "typename"
+        },
+        {
+          "kind": "text",
+          "spelling": " "
+        },
+        {
+          "kind": "genericParameter",
+          "spelling": "Y"
+        },
+        {
+          "kind": "text",
+          "spelling": "> "
+        },
+        {
+          "kind": "keyword",
+          "spelling": "class"
+        },
+        {
+          "kind": "text",
+          "spelling": " "
+        },
+        {
+          "kind": "identifier",
+          "spelling": "Foo"
+        },
+        {
+          "kind": "text",
+          "spelling": ";"
+        }
+      ],
+      "identifier": {
+        "interfaceLanguage": "c++",
+        "precise": "c:@ST>2#T#T@Foo"
+      },
+      "kind": {
+        "displayName": "Class",
+        "identifier": "c++.class"
+      },
+      "location": {
+        "position": {
+          "character": 40,
+          "line": 1
+        },
+        "uri": "file://INPUT_DIR/input.h"
+      },
+      "names": {
+        "navigator": [
+          {
+            "kind": "identifier",
+            "spelling": "Foo"
+          }
+        ],
+        "subHeading": [
+          {
+            "kind": "identifier",
+            "spelling": "Foo"
+          }
+        ],
+        "title": "Foo"
+      },
+      "pathComponents": [
+        "Foo"
+      ],
+      "swiftGenerics": {
+        "parameters": [
+          {
+            "depth": 0,
+            "index": 0,
+            "name": "X"
+          },
+          {
+            "depth": 0,
+            "index": 1,
+            "name": "Y"
+          }
+        ]
+      }
+    },
+    {
+      "accessLevel": "public",
+      "declarationFragments": [
+        {
+          "kind": "keyword",
+          "spelling": "template"
+        },
+        {
+          "kind": "text",
+          "spelling": "<"
+        },
+        {
+          "kind": "keyword",
+          "spelling": "typename"
+        },
+        {
+          "kind": "text",
+          "spelling": " "
+        },
+        {
+          "kind": "genericParameter",
+          "spelling": "Z"
+        },
+        {
+          "kind": "text",
+          "spelling": "> "
+        },
+        {
+          "kind": "keyword",
+          "spelling": "class"
+        },
+        {
+          "kind": "text",
+          "spelling": " "
+        },
+        {
+          "kind": "identifier",
+          "spelling": "Foo"
+        },
+        {
+          "kind": "text",
+          "spelling": "<"
+        },
+        {
+          "kind": "genericParameter",
+          "spelling": "Z"
+        },
+        {
+          "kind": "text",
+          "spelling": ", "
+        },
+        {
+          "kind": "typeIdentifier",
+          "preciseIdentifier": "c:I",
+          "spelling": "int"
+        },
+        {
+          "kind": "text",
+          "spelling": ">;"
+        }
+      ],
+      "identifier": {
+        "interfaceLanguage": "c++",
+        "precise": "c:@SP>1#T@Foo>#t0.0#I"
+      },
+      "kind": {
+        "displayName": "Class",
+        "identifier": "c++.class"
+      },
+      "location": {
+        "position": {
+          "character": 28,
+          "line": 3
+        },
+        "uri": "file://INPUT_DIR/input.h"
+      },
+      "names": {
+        "navigator": [
+          {
+            "kind": "identifier",
+            "spelling": "Foo"
+          }
+        ],
+        "subHeading": [
+          {
+            "kind": "identifier",
+            "spelling": "Foo"
+          }
+        ],
+        "title": "Foo"
+      },
+      "pathComponents": [
+        "Foo"
+      ],
+      "swiftGenerics": {
+        "parameters": [
+          {
+            "depth": 0,
+            "index": 0,
+            "name": "Z"
+          }
+        ]
+      }
+    }
+  ]
+}
diff --git a/clang/test/ExtractAPI/class_template_spec.cpp b/clang/test/ExtractAPI/class_template_spec.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/ExtractAPI/class_template_spec.cpp
@@ -0,0 +1,206 @@
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+// RUN: sed -e "s@INPUT_DIR@%{/t:regex_replacement}@g" \
+// RUN: %t/reference.output.json.in >> %t/reference.output.json
+// RUN: %clang_cc1 -extract-api -triple arm64-apple-macosx \
+// RUN:   -x c++-header %t/input.h -o %t/output.json -verify
+
+// Generator version is not consistent across test runs, normalize it.
+// RUN: sed -e "s@\"generator\": \".*\"@\"generator\": \"?\"@g" \
+// RUN: %t/output.json >> %t/output-normalized.json
+// RUN: diff %t/reference.output.json %t/output-normalized.json
+
+//--- input.h
+template<typename T> class Foo {};
+
+template<> class Foo<int> {};
+
+/// expected-no-diagnostics
+
+//--- reference.output.json.in
+{
+  "metadata": {
+    "formatVersion": {
+      "major": 0,
+      "minor": 5,
+      "patch": 3
+    },
+    "generator": "?"
+  },
+  "module": {
+    "name": "",
+    "platform": {
+      "architecture": "arm64",
+      "operatingSystem": {
+        "minimumVersion": {
+          "major": 11,
+          "minor": 0,
+          "patch": 0
+        },
+        "name": "macosx"
+      },
+      "vendor": "apple"
+    }
+  },
+  "relationships": [],
+  "symbols": [
+    {
+      "accessLevel": "public",
+      "declarationFragments": [
+        {
+          "kind": "keyword",
+          "spelling": "template"
+        },
+        {
+          "kind": "text",
+          "spelling": "<"
+        },
+        {
+          "kind": "keyword",
+          "spelling": "typename"
+        },
+        {
+          "kind": "text",
+          "spelling": " "
+        },
+        {
+          "kind": "genericParameter",
+          "spelling": "T"
+        },
+        {
+          "kind": "text",
+          "spelling": "> "
+        },
+        {
+          "kind": "keyword",
+          "spelling": "class"
+        },
+        {
+          "kind": "text",
+          "spelling": " "
+        },
+        {
+          "kind": "identifier",
+          "spelling": "Foo"
+        },
+        {
+          "kind": "text",
+          "spelling": ";"
+        }
+      ],
+      "identifier": {
+        "interfaceLanguage": "c++",
+        "precise": "c:@ST>1#T@Foo"
+      },
+      "kind": {
+        "displayName": "Class",
+        "identifier": "c++.class"
+      },
+      "location": {
+        "position": {
+          "character": 28,
+          "line": 1
+        },
+        "uri": "file://INPUT_DIR/input.h"
+      },
+      "names": {
+        "navigator": [
+          {
+            "kind": "identifier",
+            "spelling": "Foo"
+          }
+        ],
+        "subHeading": [
+          {
+            "kind": "identifier",
+            "spelling": "Foo"
+          }
+        ],
+        "title": "Foo"
+      },
+      "pathComponents": [
+        "Foo"
+      ],
+      "swiftGenerics": {
+        "parameters": [
+          {
+            "depth": 0,
+            "index": 0,
+            "name": "T"
+          }
+        ]
+      }
+    },
+    {
+      "accessLevel": "public",
+      "declarationFragments": [
+        {
+          "kind": "keyword",
+          "spelling": "template"
+        },
+        {
+          "kind": "text",
+          "spelling": "<> "
+        },
+        {
+          "kind": "keyword",
+          "spelling": "class"
+        },
+        {
+          "kind": "text",
+          "spelling": " "
+        },
+        {
+          "kind": "identifier",
+          "spelling": "Foo"
+        },
+        {
+          "kind": "text",
+          "spelling": "<"
+        },
+        {
+          "kind": "typeIdentifier",
+          "preciseIdentifier": "c:I",
+          "spelling": "int"
+        },
+        {
+          "kind": "text",
+          "spelling": ">;"
+        }
+      ],
+      "identifier": {
+        "interfaceLanguage": "c++",
+        "precise": "c:@S@Foo>#I"
+      },
+      "kind": {
+        "displayName": "Class",
+        "identifier": "c++.class"
+      },
+      "location": {
+        "position": {
+          "character": 18,
+          "line": 3
+        },
+        "uri": "file://INPUT_DIR/input.h"
+      },
+      "names": {
+        "navigator": [
+          {
+            "kind": "identifier",
+            "spelling": "Foo"
+          }
+        ],
+        "subHeading": [
+          {
+            "kind": "identifier",
+            "spelling": "Foo"
+          }
+        ],
+        "title": "Foo"
+      },
+      "pathComponents": [
+        "Foo"
+      ]
+    }
+  ]
+}
diff --git a/clang/test/ExtractAPI/concept.cpp b/clang/test/ExtractAPI/concept.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/ExtractAPI/concept.cpp
@@ -0,0 +1,133 @@
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+// RUN: sed -e "s@INPUT_DIR@%{/t:regex_replacement}@g" \
+// RUN: %t/reference.output.json.in >> %t/reference.output.json
+// RUN: %clang_cc1 -std=c++20 -extract-api -triple arm64-apple-macosx \
+// RUN:   -x c++-header %t/input.h -o %t/output.json -verify
+
+// Generator version is not consistent across test runs, normalize it.
+// RUN: sed -e "s@\"generator\": \".*\"@\"generator\": \"?\"@g" \
+// RUN: %t/output.json >> %t/output-normalized.json
+// RUN: diff %t/reference.output.json %t/output-normalized.json
+
+//--- input.h
+template<typename T> concept Foo = true;
+
+/// expected-no-diagnostics
+
+//--- reference.output.json.in
+{
+  "metadata": {
+    "formatVersion": {
+      "major": 0,
+      "minor": 5,
+      "patch": 3
+    },
+    "generator": "?"
+  },
+  "module": {
+    "name": "",
+    "platform": {
+      "architecture": "arm64",
+      "operatingSystem": {
+        "minimumVersion": {
+          "major": 11,
+          "minor": 0,
+          "patch": 0
+        },
+        "name": "macosx"
+      },
+      "vendor": "apple"
+    }
+  },
+  "relationships": [],
+  "symbols": [
+    {
+      "accessLevel": "public",
+      "declarationFragments": [
+        {
+          "kind": "keyword",
+          "spelling": "template"
+        },
+        {
+          "kind": "text",
+          "spelling": "<"
+        },
+        {
+          "kind": "keyword",
+          "spelling": "typename"
+        },
+        {
+          "kind": "text",
+          "spelling": " "
+        },
+        {
+          "kind": "genericParameter",
+          "spelling": "T"
+        },
+        {
+          "kind": "text",
+          "spelling": "> "
+        },
+        {
+          "kind": "keyword",
+          "spelling": "concept"
+        },
+        {
+          "kind": "text",
+          "spelling": " "
+        },
+        {
+          "kind": "identifier",
+          "spelling": "Foo"
+        },
+        {
+          "kind": "text",
+          "spelling": ";"
+        }
+      ],
+      "identifier": {
+        "interfaceLanguage": "c++",
+        "precise": "c:@CT@Foo"
+      },
+      "kind": {
+        "displayName": "Concept",
+        "identifier": "c++.concept"
+      },
+      "location": {
+        "position": {
+          "character": 30,
+          "line": 1
+        },
+        "uri": "file://INPUT_DIR/input.h"
+      },
+      "names": {
+        "navigator": [
+          {
+            "kind": "identifier",
+            "spelling": "Foo"
+          }
+        ],
+        "subHeading": [
+          {
+            "kind": "identifier",
+            "spelling": "Foo"
+          }
+        ],
+        "title": "Foo"
+      },
+      "pathComponents": [
+        "Foo"
+      ],
+      "swiftGenerics": {
+        "parameters": [
+          {
+            "depth": 0,
+            "index": 0,
+            "name": "T"
+          }
+        ]
+      }
+    }
+  ]
+}