diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -370,6 +370,10 @@
 - Clang now diagnoses unexpected tokens after a
   ``#pragma clang|GCC diagnostic push|pop`` directive.
   (`#13920: <https://github.com/llvm/llvm-project/issues/13920>`_)
+- A new diagnostic warning group ``deprecated-redundant-constexpr-static-def`` is
+  added. This is to be used to control warnings about out-of-line definitions of
+  static constexpr members that are unnecessary with ``-std=C++17`` onwards. The
+  diagnostic was previously only controllable via `-Wdeprecated`.
 
 Bug Fixes in This Version
 -------------------------
diff --git a/clang/include/clang/Basic/DiagnosticGroups.td b/clang/include/clang/Basic/DiagnosticGroups.td
--- a/clang/include/clang/Basic/DiagnosticGroups.td
+++ b/clang/include/clang/Basic/DiagnosticGroups.td
@@ -186,6 +186,7 @@
 // For compatibility with GCC.
 def : DiagGroup<"deprecated-copy-dtor", [DeprecatedCopyWithDtor]>;
 def DeprecatedDeclarations : DiagGroup<"deprecated-declarations">;
+def DeprecatedRedundantConstexprStaticDef : DiagGroup<"deprecated-redundant-constexpr-static-def">;
 def UnavailableDeclarations : DiagGroup<"unavailable-declarations">;
 def UnguardedAvailabilityNew : DiagGroup<"unguarded-availability-new">;
 def UnguardedAvailability : DiagGroup<"unguarded-availability",
@@ -224,7 +225,9 @@
                                           DeprecatedThisCapture,
                                           DeprecatedType,
                                           DeprecatedVolatile,
-                                          DeprecatedWritableStr]>,
+                                          DeprecatedWritableStr,
+                                          DeprecatedRedundantConstexprStaticDef,
+                                          ]>,
                  DiagCategory<"Deprecations">;
 
 def CXX20Designator : DiagGroup<"c++20-designator">;
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -450,7 +450,7 @@
 def warn_deprecated_redundant_constexpr_static_def : Warning<
   "out-of-line definition of constexpr static data member is redundant "
   "in C++17 and is deprecated">,
-  InGroup<Deprecated>, DefaultIgnore;
+  InGroup<DeprecatedRedundantConstexprStaticDef>, DefaultIgnore;
 
 def warn_decl_shadow :
   Warning<"declaration shadows a %select{"
diff --git a/clang/test/SemaCXX/redundant-out-of-line-static-constexpr-member-def-diag.cpp b/clang/test/SemaCXX/redundant-out-of-line-static-constexpr-member-def-diag.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/SemaCXX/redundant-out-of-line-static-constexpr-member-def-diag.cpp
@@ -0,0 +1,10 @@
+// RUN: %clang_cc1 -std=c++17 -verify %s -Werror -Wdeprecated -Wno-error=deprecated-redundant-constexpr-static-def
+
+namespace {
+  struct A {
+    static constexpr int n = 0;
+    static constexpr int m = 0;
+  };
+  constexpr int A::n; // expected-warning{{out-of-line definition of constexpr static data member is redundant in C++17 and is deprecated}}
+  const int A::m; // expected-warning{{out-of-line definition of constexpr static data member is redundant in C++17 and is deprecated}}
+}