diff --git a/clang/include/clang/Basic/Attr.td b/clang/include/clang/Basic/Attr.td
--- a/clang/include/clang/Basic/Attr.td
+++ b/clang/include/clang/Basic/Attr.td
@@ -1794,6 +1794,13 @@
   let SimpleHandler = 1;
 }
 
+def UnnamedAddr : InheritableAttr {
+  let Spellings = [Clang<"unnamed_addr">];
+  let Subjects = SubjectList<[GlobalVar], ErrorDiag>;
+  let Documentation = [UnnamedAddrDocs];
+  let SimpleHandler = 1;
+}
+
 def ReturnsTwice : InheritableAttr {
   let Spellings = [GCC<"returns_twice">];
   let Subjects = SubjectList<[Function]>;
diff --git a/clang/include/clang/Basic/AttrDocs.td b/clang/include/clang/Basic/AttrDocs.td
--- a/clang/include/clang/Basic/AttrDocs.td
+++ b/clang/include/clang/Basic/AttrDocs.td
@@ -1408,6 +1408,24 @@
   }];
 }
 
+def UnnamedAddrDocs : Documentation {
+  let Category = DocCatField;
+  let Content = [{
+The ``clang::unnamed_addr`` attribute specifies that the address of a global is
+not significant. This allows global constants with the same contents to be
+merged. This can break global pointer identity, i.e. two different globals have
+the same address.
+
+Example usage:
+
+.. code-block:: c
+
+  // i and j may have the same address.
+  [[clang::unnamed_addr]] const int i = 42;
+  [[clang::unnamed_addr]] const int j = 42;
+  }];
+}
+
 def ObjCRequiresSuperDocs : Documentation {
   let Category = DocCatFunction;
   let Content = [{
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
@@ -3587,6 +3587,9 @@
   "weakref declaration of %0 must be in a global context">;
 def err_attribute_weakref_without_alias : Error<
   "weakref declaration of %0 must also have an alias attribute">;
+def warn_attribute_unnamed_addr : Warning<
+  "unnamed_addr should only be used on const POD (plain old data) globals">,
+  InGroup<DiagGroup<"unnamed-addr">>;
 def err_alias_not_supported_on_darwin : Error <
   "aliases are not supported on darwin">;
 def warn_attribute_wrong_decl_type_str : Warning<
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -5255,6 +5255,9 @@
       GV->setConstant(true);
   }
 
+  if (D->hasAttr<UnnamedAddrAttr>())
+    GV->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global);
+
   CharUnits AlignVal = getContext().getDeclAlign(D);
   // Check for alignment specifed in an 'omp allocate' directive.
   if (std::optional<CharUnits> AlignValFromAllocate =
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -14519,6 +14519,13 @@
           PragmaClangRelroSection.PragmaLocation));
   }
 
+  if (VD->hasGlobalStorage() && VD->isThisDeclarationADefinition() &&
+      VD->hasAttr<UnnamedAddrAttr>() &&
+      (!VD->getType().isPODType(getASTContext()) ||
+       !VD->getType().isConstQualified())) {
+    Diag(VD->getLocation(), diag::warn_attribute_unnamed_addr);
+  }
+
   if (auto *DD = dyn_cast<DecompositionDecl>(ThisDecl)) {
     for (auto *BD : DD->bindings()) {
       FinalizeDeclaration(BD);
diff --git a/clang/test/CodeGen/unnamed-addr.c b/clang/test/CodeGen/unnamed-addr.c
new file mode 100644
--- /dev/null
+++ b/clang/test/CodeGen/unnamed-addr.c
@@ -0,0 +1,5 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-unknown -O1 -emit-llvm -o - -disable-llvm-passes %s | FileCheck %s
+
+// CHECK: @i = unnamed_addr constant i32 8
+
+[[clang::unnamed_addr]] const int i = 8;
diff --git a/clang/test/SemaCXX/unnamed-addr.cpp b/clang/test/SemaCXX/unnamed-addr.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/SemaCXX/unnamed-addr.cpp
@@ -0,0 +1,20 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+struct Foo {
+  int a;
+};
+
+struct Bar {
+  int a;
+  Bar();
+};
+
+[[clang::unnamed_addr]] const int i = 8;
+
+[[clang::unnamed_addr]] int i2 = 8; // expected-warning{{unnamed_addr should only be used on const POD (plain old data) globals}}
+
+[[clang::unnamed_addr]] const Foo j = {2};
+
+[[clang::unnamed_addr]] Foo j2 = {2}; // expected-warning{{unnamed_addr should only be used on const POD (plain old data) globals}}
+
+[[clang::unnamed_addr]] const Bar k; // expected-warning{{unnamed_addr should only be used on const POD (plain old data) globals}}