diff --git a/include/clang/Basic/Attr.td b/include/clang/Basic/Attr.td
index fd8372bab5..143b6ceb45 100644
--- a/include/clang/Basic/Attr.td
+++ b/include/clang/Basic/Attr.td
@@ -1936,7 +1936,8 @@ def ObjCRequiresPropertyDefs : InheritableAttr {
 }
 
 def Unused : InheritableAttr {
-  let Spellings = [CXX11<"", "maybe_unused", 201603>, GCC<"unused">];
+  let Spellings = [CXX11<"", "maybe_unused", 201603>, GCC<"unused">,
+                   C2x<"", "maybe_unused">];
   let Subjects = SubjectList<[Var, ObjCIvar, Type, Enum, EnumConstant, Label,
                               Field, ObjCMethod, FunctionLike], WarnDiag,
                              "ExpectedForMaybeUnused">;
diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index 5e7ed2d59e..c92d0aa8f9 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -79,7 +79,8 @@ static void DiagnoseUnusedOfDecl(Sema &S, NamedDecl *D, SourceLocation Loc) {
   if (const auto *A = D->getAttr<UnusedAttr>()) {
     // [[maybe_unused]] should not diagnose uses, but __attribute__((unused))
     // should diagnose them.
-    if (A->getSemanticSpelling() != UnusedAttr::CXX11_maybe_unused) {
+    if (A->getSemanticSpelling() != UnusedAttr::CXX11_maybe_unused &&
+        A->getSemanticSpelling() != UnusedAttr::C2x_maybe_unused) {
       const Decl *DC = cast_or_null<Decl>(S.getCurObjCLexicalContext());
       if (DC && !DC->hasAttr<UnusedAttr>())
         S.Diag(Loc, diag::warn_used_but_marked_unused) << D->getDeclName();
diff --git a/test/Sema/c2x-maybe_unused-errors.c b/test/Sema/c2x-maybe_unused-errors.c
new file mode 100644
index 0000000000..68150dded9
--- /dev/null
+++ b/test/Sema/c2x-maybe_unused-errors.c
@@ -0,0 +1,12 @@
+// RUN: %clang_cc1 -fsyntax-only -Wunused -fdouble-square-bracket-attributes -verify %s
+
+struct [[maybe_unused]] S1 { // ok
+  int a [[maybe_unused]];
+};
+struct [[maybe_unused maybe_unused]] S2 { // expected-error {{attribute 'maybe_unused' cannot appear multiple times in an attribute specifier}}
+  int a;
+};
+struct [[maybe_unused("Wrong")]] S3 { // expected-error {{'maybe_unused' cannot have an argument list}}
+  int a;
+};
+
diff --git a/test/Sema/c2x-maybe_unused.c b/test/Sema/c2x-maybe_unused.c
new file mode 100644
index 0000000000..816cf7835f
--- /dev/null
+++ b/test/Sema/c2x-maybe_unused.c
@@ -0,0 +1,35 @@
+// RUN: %clang_cc1 -fsyntax-only -Wunused -fdouble-square-bracket-attributes -verify %s
+
+struct [[maybe_unused]] S1 { // ok
+  int a [[maybe_unused]];
+};
+
+enum [[maybe_unused]] E1 {
+  EnumVal [[maybe_unused]]
+};
+
+[[maybe_unused]] void unused_func([[maybe_unused]] int parm) {
+  typedef int maybe_unused_int [[maybe_unused]];
+  [[maybe_unused]] int I;
+}
+
+void f1(void) {
+  int x; // expected-warning {{unused variable}}
+  typedef int I; // expected-warning {{unused typedef 'I'}}
+
+  // Should not warn about these due to not being used.
+  [[maybe_unused]] int y;
+  typedef int maybe_unused_int [[maybe_unused]];
+
+  // Should not warn about these uses.
+  struct S1 s;
+  maybe_unused_int test;
+  y = 12;
+}
+
+void f2(void);
+[[maybe_unused]] void f2(void);
+
+void f2(void) {
+}
+