diff --git a/clang/include/clang/Basic/DiagnosticParseKinds.td b/clang/include/clang/Basic/DiagnosticParseKinds.td
index e5e071f43fa75..2e3a0dfbf6d53 100644
--- a/clang/include/clang/Basic/DiagnosticParseKinds.td
+++ b/clang/include/clang/Basic/DiagnosticParseKinds.td
@@ -399,6 +399,8 @@ def err_requires_clause_on_declarator_not_declaring_a_function : Error<
   "trailing requires clause can only be used when declaring a function">;
 def err_requires_clause_inside_parens : Error<
   "trailing requires clause should be placed outside parentheses">;
+def err_auto_type_specifier : Error<
+  "'auto' cannot be combined with a type specifier">;
 def ext_auto_storage_class : ExtWarn<
   "'auto' storage class specifier is not permitted in C++11, and will not "
   "be supported in future releases">, InGroup<DiagGroup<"auto-storage-class">>;
diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
index 7e4a164e34eda..b8741145a697f 100644
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -4095,11 +4095,23 @@ void Parser::ParseDeclarationSpecifiers(
     case tok::kw_auto:
       if (getLangOpts().CPlusPlus11 || getLangOpts().C23) {
         if (isKnownToBeTypeSpecifier(GetLookAheadToken(1))) {
-          isInvalid = DS.SetStorageClassSpec(Actions, DeclSpec::SCS_auto, Loc,
-                                             PrevSpec, DiagID, Policy);
-          if (!isInvalid && !getLangOpts().C23)
-            Diag(Tok, diag::ext_auto_storage_class)
-              << FixItHint::CreateRemoval(DS.getStorageClassSpecLoc());
+          // In C++ (not C23), 'auto' cannot be combined with a type specifier.
+          // OpenCL is excluded here because Sema emits a more specific error
+          // message for OpenCL (e.g., "does not support the 'auto' storage
+          // class specifier").
+          if (!getLangOpts().C23 && !getLangOpts().OpenCLCPlusPlus) {
+            // In C++11+, 'auto' cannot be combined with a type specifier.
+            // Don't set the storage class specifier to avoid Sema emitting a
+            // redundant error (GCC only emits one error for this case: "two or
+            // more data types in declaration").
+            isInvalid = true;
+            PrevSpec = "auto";
+            DiagID = diag::err_auto_type_specifier;
+          } else {
+            // C23 allows 'auto' as storage class with type specifier.
+            isInvalid = DS.SetStorageClassSpec(Actions, DeclSpec::SCS_auto, Loc,
+                                               PrevSpec, DiagID, Policy);
+          }
         } else
           isInvalid = DS.SetTypeSpecType(DeclSpec::TST_auto, Loc, PrevSpec,
                                          DiagID, Policy);
diff --git a/clang/test/CXX/dcl.dcl/dcl.spec/dcl.stc/p2.cpp b/clang/test/CXX/dcl.dcl/dcl.spec/dcl.stc/p2.cpp
index 723a79628116c..da252d11175ab 100644
--- a/clang/test/CXX/dcl.dcl/dcl.spec/dcl.stc/p2.cpp
+++ b/clang/test/CXX/dcl.dcl/dcl.spec/dcl.stc/p2.cpp
@@ -5,14 +5,18 @@
 // The auto or register specifiers can be applied only to names of objects
 // declared in a block (6.3) or to function parameters (8.4).
 
-auto int ao; // expected-error {{illegal storage class on file-scoped variable}}
+auto int ao;
 #if __cplusplus >= 201103L // C++11 or later
-// expected-warning@-2 {{'auto' storage class specifier is not permitted in C++11, and will not be supported in future releases}}
+// expected-error@-2 {{'auto' cannot be combined with a type specifier}}
+#else
+// expected-error@-4 {{illegal storage class on file-scoped variable}}
 #endif
 
-auto void af(); // expected-error {{illegal storage class on function}}
+auto void af();
 #if __cplusplus >= 201103L // C++11 or later
-// expected-warning@-2 {{'auto' storage class specifier is not permitted in C++11, and will not be supported in future releases}}
+// expected-error@-2 {{'auto' cannot be combined with a type specifier}}
+#else
+// expected-error@-4 {{illegal storage class on function}}
 #endif
 
 register int ro; // expected-error {{illegal storage class on file-scoped variable}}
@@ -25,13 +29,17 @@ register int ro; // expected-error {{illegal storage class on file-scoped variab
 register void rf(); // expected-error {{illegal storage class on function}}
 
 struct S {
-  auto int ao; // expected-error {{storage class specified for a member declaration}}
+  auto int ao;
 #if __cplusplus >= 201103L // C++11 or later
-// expected-warning@-2 {{'auto' storage class specifier is not permitted in C++11, and will not be supported in future releases}}
+// expected-error@-2 {{'auto' cannot be combined with a type specifier}}
+#else
+// expected-error@-4 {{storage class specified for a member declaration}}
 #endif
-  auto void af(); // expected-error {{storage class specified for a member declaration}}
+  auto void af();
 #if __cplusplus >= 201103L // C++11 or later
-// expected-warning@-2 {{'auto' storage class specifier is not permitted in C++11, and will not be supported in future releases}}
+// expected-error@-2 {{'auto' cannot be combined with a type specifier}}
+#else
+// expected-error@-4 {{storage class specified for a member declaration}}
 #endif
 
   register int ro; // expected-error {{storage class specified for a member declaration}}
@@ -40,19 +48,21 @@ struct S {
 
 void foo(auto int ap, register int rp) {
 #if __cplusplus >= 201703L
-// expected-warning@-2 {{'auto' storage class specifier is not permitted in C++11, and will not be supported in future releases}}
+// expected-error@-2 {{'auto' cannot be combined with a type specifier}}
 // expected-error@-3 {{ISO C++17 does not allow 'register' storage class specifier}}
 #elif __cplusplus >= 201103L
-// expected-warning@-5 {{'auto' storage class specifier is not permitted in C++11, and will not be supported in future releases}}
+// expected-error@-5 {{'auto' cannot be combined with a type specifier}}
 // expected-warning@-6 {{'register' storage class specifier is deprecated}}
 #endif
   auto int abo;
 #if __cplusplus >= 201103L // C++11 or later
-// expected-warning@-2 {{'auto' storage class specifier is not permitted in C++11, and will not be supported in future releases}}
+// expected-error@-2 {{'auto' cannot be combined with a type specifier}}
 #endif
-  auto void abf(); // expected-error {{illegal storage class on function}}
+  auto void abf();
 #if __cplusplus >= 201103L // C++11 or later
-// expected-warning@-2 {{'auto' storage class specifier is not permitted in C++11, and will not be supported in future releases}}
+// expected-error@-2 {{'auto' cannot be combined with a type specifier}}
+#else
+// expected-error@-4 {{illegal storage class on function}}
 #endif
 
   register int rbo;
diff --git a/clang/test/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.spec.auto/p3-1y.cpp b/clang/test/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.spec.auto/p3-1y.cpp
index e8f12156a4242..907765780d069 100644
--- a/clang/test/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.spec.auto/p3-1y.cpp
+++ b/clang/test/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.spec.auto/p3-1y.cpp
@@ -56,7 +56,7 @@ namespace p3_example {
   auto x = 5;
   const auto *v = &x, u = 6;
   static auto y = 0.0;
-  auto int r;  // expected-warning {{storage class}} expected-error {{file-scope}}
+  auto int r;  // expected-error {{'auto' cannot be combined with a type specifier}}
 
   static_assert(is_same<decltype(x), int>(), "");
   static_assert(is_same<decltype(v), const int*>(), "");
diff --git a/clang/test/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.spec.auto/p3.cpp b/clang/test/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.spec.auto/p3.cpp
index 440c78201293b..8d7765523461c 100644
--- a/clang/test/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.spec.auto/p3.cpp
+++ b/clang/test/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.spec.auto/p3.cpp
@@ -42,7 +42,12 @@ void p3example() {
   static auto y = 0.0;
   // In C++98: 'auto' storage class specifier is redundant and incompatible with C++0x
   // In C++0x: 'auto' storage class specifier is not permitted in C++0x, and will not be supported in future releases
-  auto int r; // expected-warning {{'auto' storage class specifier}}
+  auto int r;
+#if __cplusplus >= 201103L
+  // expected-error@-2 {{'auto' cannot be combined with a type specifier}}
+#else
+  // expected-warning@-4 {{'auto' storage class specifier}}
+#endif
 
   same<__typeof(x), int> xHasTypeInt;
   same<__typeof(v), const int*> vHasTypeConstIntPtr;
diff --git a/clang/test/CXX/drs/cwg3xx.cpp b/clang/test/CXX/drs/cwg3xx.cpp
index bbd87c060801a..2e735df3d8d78 100644
--- a/clang/test/CXX/drs/cwg3xx.cpp
+++ b/clang/test/CXX/drs/cwg3xx.cpp
@@ -1732,11 +1732,13 @@ namespace cwg395 { // cwg395: 3.0
 namespace cwg396 { // cwg396: 3.0
   void f() {
     auto int a();
-    // since-cxx11-error@-1 {{'auto' storage class specifier is not permitted in C++11, and will not be supported in future releases}}
-    // expected-error@-2 {{illegal storage class on function}}
+    // cxx98-error@-1 {{illegal storage class on function}}
+    // since-cxx11-error@-2 {{'auto' cannot be combined with a type specifier}}
+    // since-cxx11-warning@-3 {{empty parentheses interpreted as a function declaration}}
+    // since-cxx11-note@-4 {{replace parentheses with an initializer to declare a variable}}
     int (i); // #cwg396-i
     auto int (i);
-    // since-cxx11-error@-1 {{'auto' storage class specifier is not permitted in C++11, and will not be supported in future releases}}
+    // since-cxx11-error@-1 {{'auto' cannot be combined with a type specifier}}
     // expected-error@-2 {{redefinition of 'i'}}
     //   expected-note@#cwg396-i {{previous definition is here}}
   }
diff --git a/clang/test/Parser/cxx-auto-type-specifier.cpp b/clang/test/Parser/cxx-auto-type-specifier.cpp
new file mode 100644
index 0000000000000..689e25abdea05
--- /dev/null
+++ b/clang/test/Parser/cxx-auto-type-specifier.cpp
@@ -0,0 +1,22 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++14 %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++17 %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++20 %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++23 %s
+
+// Test that 'auto' cannot be combined with a type specifier in C++.
+void f() {
+  auto int x = 1;        // expected-error {{'auto' cannot be combined with a type specifier}}
+  auto char c = 'a';    // expected-error {{'auto' cannot be combined with a type specifier}}
+  auto float f = 1.0f;  // expected-error {{'auto' cannot be combined with a type specifier}}
+  auto double d = 1.0;   // expected-error {{'auto' cannot be combined with a type specifier}}
+  auto long l = 1L;     // expected-error {{'auto' cannot be combined with a type specifier}}
+}
+
+// Test that regular 'auto' (type deduction) still works in C++.
+void h() {
+  auto x = 1;
+  auto y = 2.0;
+  auto z = 'c';
+}
+
diff --git a/clang/test/SemaCXX/auto-cxx0x.cpp b/clang/test/SemaCXX/auto-cxx0x.cpp
index 07687b6066790..8282444b1e96e 100644
--- a/clang/test/SemaCXX/auto-cxx0x.cpp
+++ b/clang/test/SemaCXX/auto-cxx0x.cpp
@@ -1,7 +1,7 @@
 // RUN: %clang_cc1 -fsyntax-only -verify %s -std=c++11
 // RUN: %clang_cc1 -fsyntax-only -verify %s -std=c++1y
 void f() {
-  auto int a; // expected-warning {{'auto' storage class specifier is not permitted in C++11, and will not be supported in future releases}}
+  auto int a; // expected-error {{'auto' cannot be combined with a type specifier}}
   int auto b; // expected-error{{cannot combine with previous 'int' declaration specifier}}
 }
 
diff --git a/clang/test/SemaCXX/class.cpp b/clang/test/SemaCXX/class.cpp
index f1e02d5158aac..fae85db68ddc4 100644
--- a/clang/test/SemaCXX/class.cpp
+++ b/clang/test/SemaCXX/class.cpp
@@ -2,11 +2,12 @@
 // RUN: %clang_cc1 -fsyntax-only -verify=expected,cxx98 -Wc++11-compat %s -std=c++98
 class C {
 public:
-  auto int errx; // expected-error {{storage class specified for a member declaration}}
+  auto int errx;
 #if __cplusplus <= 199711L
-  // expected-warning@-2 {{'auto' storage class specifier is redundant}}
+  // expected-error@-2 {{storage class specified for a member declaration}}
+  // expected-warning@-3 {{'auto' storage class specifier is redundant and incompatible with C++11}}
 #else
-  // expected-warning@-4 {{'auto' storage class specifier is not permitted in C++11, and will not be supported in future releases}}
+  // expected-error@-5 {{'auto' cannot be combined with a type specifier}}
 #endif
   register int erry; // expected-error {{storage class specified for a member declaration}}
   extern int errz; // expected-error {{storage class specified for a member declaration}}
diff --git a/clang/test/SemaCXX/static-data-member.cpp b/clang/test/SemaCXX/static-data-member.cpp
index fb63da9b40099..2dbcae1745e5b 100644
--- a/clang/test/SemaCXX/static-data-member.cpp
+++ b/clang/test/SemaCXX/static-data-member.cpp
@@ -13,7 +13,12 @@ double ABC::a = 1.0;
 extern double ABC::b = 1.0; // expected-error {{static data member definition cannot specify a storage class}}
 static double ABC::c = 1.0;  // expected-error {{'static' can only be specified inside the class definition}}
 __private_extern__ double ABC::d = 1.0; // expected-error {{static data member definition cannot specify a storage class}}
-auto double ABC::e = 1.0; // expected-error {{static data member definition cannot specify a storage class}}
+auto double ABC::e = 1.0;
+#if __cplusplus >= 201103L
+// expected-error@-2 {{'auto' cannot be combined with a type specifier}}
+#else
+// expected-error@-4 {{static data member definition cannot specify a storage class}}
+#endif
 #if __cplusplus < 201703L
 register double ABC::f = 1.0; // expected-error {{static data member definition cannot specify a storage class}}
 #endif