diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 7185a4d6cab058..659f1d6df39e46 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -5046,8 +5046,8 @@ def err_unexpanded_parameter_pack : Error<
   "size|static assertion|fixed underlying type|enumerator value|"
   "using declaration|friend declaration|qualifier|initializer|default argument|"
   "non-type template parameter type|exception type|partial specialization|"
-  "__if_exists name|__if_not_exists name|lambda|block|type constraint}0 "
-  "contains%plural{0: an|:}1 unexpanded parameter pack"
+  "__if_exists name|__if_not_exists name|lambda|block|type constraint|"
+  "requirement}0 contains%plural{0: an|:}1 unexpanded parameter pack"
   "%plural{0:|1: %2|2:s %2 and %3|:s %2, %3, ...}1">;
 
 def err_pack_expansion_without_parameter_packs : Error<
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index b88e5578c1140c..09e4c6743efc9e 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -7760,11 +7760,14 @@ class Sema final {
     /// Lambda expression.
     UPPC_Lambda,
 
-    /// Block expression,
+    /// Block expression.
     UPPC_Block,
 
-    /// A type constraint,
-    UPPC_TypeConstraint
+    /// A type constraint.
+    UPPC_TypeConstraint,
+
+    // A requirement in a requires-expression.
+    UPPC_Requirement,
   };
 
   /// Diagnose unexpanded parameter packs.
@@ -7803,6 +7806,15 @@ class Sema final {
   bool DiagnoseUnexpandedParameterPack(Expr *E,
                        UnexpandedParameterPackContext UPPC = UPPC_Expression);
 
+  /// If the given requirees-expression contains an unexpanded reference to one
+  /// of its own parameter packs, diagnose the error.
+  ///
+  /// \param RE The requiress-expression that is being checked for unexpanded
+  /// parameter packs.
+  ///
+  /// \returns true if an error occurred, false otherwise.
+  bool DiagnoseUnexpandedParameterPackInRequiresExpr(RequiresExpr *RE);
+
   /// If the given nested-name-specifier contains an unexpanded
   /// parameter pack, diagnose the error.
   ///
diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index fe5ba6a5e87f60..335ee95715d0ce 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -8650,6 +8650,9 @@ Sema::ActOnRequiresExpr(SourceLocation RequiresKWLoc,
                         ArrayRef<ParmVarDecl *> LocalParameters,
                         ArrayRef<concepts::Requirement *> Requirements,
                         SourceLocation ClosingBraceLoc) {
-  return RequiresExpr::Create(Context, RequiresKWLoc, Body, LocalParameters,
-                              Requirements, ClosingBraceLoc);
+  auto *RE = RequiresExpr::Create(Context, RequiresKWLoc, Body, LocalParameters,
+                                  Requirements, ClosingBraceLoc);
+  if (DiagnoseUnexpandedParameterPackInRequiresExpr(RE))
+    return ExprError();
+  return RE;
 }
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 5d037e58de51e8..d63d307b9ab7c0 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -8476,6 +8476,9 @@ Decl *Sema::ActOnConceptDefinition(Scope *S,
     return nullptr;
   }
 
+  if (DiagnoseUnexpandedParameterPack(ConstraintExpr))
+    return nullptr;
+
   ConceptDecl *NewDecl = ConceptDecl::Create(Context, DC, NameLoc, Name,
                                              TemplateParameterLists.front(),
                                              ConstraintExpr);
diff --git a/clang/lib/Sema/SemaTemplateVariadic.cpp b/clang/lib/Sema/SemaTemplateVariadic.cpp
index c95d67b7c73201..623d808b59f68c 100644
--- a/clang/lib/Sema/SemaTemplateVariadic.cpp
+++ b/clang/lib/Sema/SemaTemplateVariadic.cpp
@@ -408,6 +408,29 @@ bool Sema::DiagnoseUnexpandedParameterPack(Expr *E,
   return DiagnoseUnexpandedParameterPacks(E->getBeginLoc(), UPPC, Unexpanded);
 }
 
+bool Sema::DiagnoseUnexpandedParameterPackInRequiresExpr(RequiresExpr *RE) {
+  if (!RE->containsUnexpandedParameterPack())
+    return false;
+
+  SmallVector<UnexpandedParameterPack, 2> Unexpanded;
+  CollectUnexpandedParameterPacksVisitor(Unexpanded).TraverseStmt(RE);
+  assert(!Unexpanded.empty() && "Unable to find unexpanded parameter packs");
+
+  // We only care about unexpanded references to the RequiresExpr's own
+  // parameter packs.
+  auto Parms = RE->getLocalParameters();
+  llvm::SmallPtrSet<NamedDecl*, 8> ParmSet(Parms.begin(), Parms.end());
+  SmallVector<UnexpandedParameterPack, 2> UnexpandedParms;
+  for (auto Parm : Unexpanded)
+    if (ParmSet.contains(Parm.first.dyn_cast<NamedDecl*>()))
+      UnexpandedParms.push_back(Parm);
+  if (UnexpandedParms.empty())
+    return false;
+
+  return DiagnoseUnexpandedParameterPacks(RE->getBeginLoc(), UPPC_Requirement,
+                                          UnexpandedParms);
+}
+
 bool Sema::DiagnoseUnexpandedParameterPack(const CXXScopeSpec &SS,
                                         UnexpandedParameterPackContext UPPC) {
   // C++0x [temp.variadic]p5:
diff --git a/clang/test/SemaTemplate/concepts.cpp b/clang/test/SemaTemplate/concepts.cpp
new file mode 100644
index 00000000000000..db154a9a0f5b51
--- /dev/null
+++ b/clang/test/SemaTemplate/concepts.cpp
@@ -0,0 +1,25 @@
+// RUN: %clang_cc1 -std=c++20 -verify %s
+
+namespace PR47043 {
+  template<typename T> concept True = true;
+  template<typename ...T> concept AllTrue1 = True<T>; // expected-error {{expression contains unexpanded parameter pack 'T'}}
+  template<typename ...T> concept AllTrue2 = (True<T> && ...);
+  static_assert(AllTrue2<int, float, char>);
+}
+
+namespace PR47025 {
+  template<typename ...T> concept AllAddable1 = requires(T ...t) { (void(t + 1), ...); };
+  template<typename ...T> concept AllAddable2 = (requires(T ...t) { (t + 1); } && ...); // expected-error {{requirement contains unexpanded parameter pack 't'}}
+  template<typename ...T> concept AllAddable3 = (requires(T t) { (t + 1); } && ...);
+  template<typename ...T> concept AllAddable4 = requires(T t) { (t + 1); }; // expected-error {{expression contains unexpanded parameter pack 'T'}}
+  template<typename ...T> concept AllAddable5 = requires(T t) { (void(t + 1), ...); }; // expected-error {{does not contain any unexpanded}}
+  template<typename ...T> concept AllAddable6 = (requires { (T() + 1); } && ...);
+  template<typename ...T> concept AllAddable7 = requires { (T() + 1); }; // expected-error {{expression contains unexpanded parameter pack 'T'}}
+
+  static_assert(AllAddable1<int, float>);
+  static_assert(AllAddable3<int, float>);
+  static_assert(AllAddable6<int, float>);
+  static_assert(!AllAddable1<int, void>);
+  static_assert(!AllAddable3<int, void>);
+  static_assert(!AllAddable6<int, void>);
+}