diff --git a/libcxx/include/__availability b/libcxx/include/__availability
--- a/libcxx/include/__availability
+++ b/libcxx/include/__availability
@@ -172,6 +172,8 @@
     // be avoided.
 // #   define _LIBCPP_HAS_NO_VERBOSE_ABORT_IN_LIBRARY
 
+#  define _LIBCPP_AVAILABILITY_MEMORY_RESOURCE
+
 #elif defined(__APPLE__)
 
 #   define _LIBCPP_AVAILABILITY_SHARED_MUTEX                                    \
@@ -273,6 +275,8 @@
 
 #   define _LIBCPP_HAS_NO_VERBOSE_ABORT_IN_LIBRARY
 
+#  define _LIBCPP_AVAILABILITY_MEMORY_RESOURCE __attribute__((__unavailable__))
+
 #else
 
 // ...New vendors can add availability markup here...
diff --git a/libcxx/include/__memory_resource/memory_resource.h b/libcxx/include/__memory_resource/memory_resource.h
--- a/libcxx/include/__memory_resource/memory_resource.h
+++ b/libcxx/include/__memory_resource/memory_resource.h
@@ -26,7 +26,7 @@
 
 _LIBCPP_DIAGNOSTIC_PUSH
 _LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wweak-vtables") // TODO: move destructor into the dylib
-class _LIBCPP_TYPE_VIS memory_resource {
+class _LIBCPP_TYPE_VIS _LIBCPP_AVAILABILITY_MEMORY_RESOURCE memory_resource {
   static const size_t __max_align = alignof(max_align_t);
 
 public:
@@ -61,13 +61,10 @@
 
 // [mem.res.global]
 
-_LIBCPP_FUNC_VIS memory_resource* get_default_resource() noexcept;
-
-_LIBCPP_FUNC_VIS memory_resource* set_default_resource(memory_resource*) noexcept;
-
-_LIBCPP_FUNC_VIS memory_resource* new_delete_resource() noexcept;
-
-_LIBCPP_FUNC_VIS memory_resource* null_memory_resource() noexcept;
+_LIBCPP_AVAILABILITY_MEMORY_RESOURCE _LIBCPP_FUNC_VIS memory_resource* get_default_resource() noexcept;
+_LIBCPP_AVAILABILITY_MEMORY_RESOURCE _LIBCPP_FUNC_VIS memory_resource* set_default_resource(memory_resource*) noexcept;
+_LIBCPP_AVAILABILITY_MEMORY_RESOURCE _LIBCPP_FUNC_VIS memory_resource* new_delete_resource() noexcept;
+_LIBCPP_AVAILABILITY_MEMORY_RESOURCE _LIBCPP_FUNC_VIS memory_resource* null_memory_resource() noexcept;
 
 } // namespace pmr
 
diff --git a/libcxx/include/__memory_resource/monotonic_buffer_resource.h b/libcxx/include/__memory_resource/monotonic_buffer_resource.h
--- a/libcxx/include/__memory_resource/monotonic_buffer_resource.h
+++ b/libcxx/include/__memory_resource/monotonic_buffer_resource.h
@@ -26,7 +26,7 @@
 
 // [mem.res.monotonic.buffer]
 
-class _LIBCPP_TYPE_VIS monotonic_buffer_resource : public memory_resource {
+class _LIBCPP_TYPE_VIS _LIBCPP_AVAILABILITY_MEMORY_RESOURCE monotonic_buffer_resource : public memory_resource {
   static const size_t __default_buffer_capacity  = 1024;
   static const size_t __default_buffer_alignment = 16;
 
diff --git a/libcxx/include/__memory_resource/polymorphic_allocator.h b/libcxx/include/__memory_resource/polymorphic_allocator.h
--- a/libcxx/include/__memory_resource/polymorphic_allocator.h
+++ b/libcxx/include/__memory_resource/polymorphic_allocator.h
@@ -34,7 +34,7 @@
 // [mem.poly.allocator.class]
 
 template <class _ValueType>
-class _LIBCPP_TEMPLATE_VIS polymorphic_allocator {
+class _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_MEMORY_RESOURCE polymorphic_allocator {
 public:
   using value_type = _ValueType;
 
diff --git a/libcxx/include/__memory_resource/synchronized_pool_resource.h b/libcxx/include/__memory_resource/synchronized_pool_resource.h
--- a/libcxx/include/__memory_resource/synchronized_pool_resource.h
+++ b/libcxx/include/__memory_resource/synchronized_pool_resource.h
@@ -30,7 +30,7 @@
 
 // [mem.res.pool.overview]
 
-class _LIBCPP_TYPE_VIS synchronized_pool_resource : public memory_resource {
+class _LIBCPP_TYPE_VIS _LIBCPP_AVAILABILITY_MEMORY_RESOURCE synchronized_pool_resource : public memory_resource {
 public:
   _LIBCPP_HIDE_FROM_ABI synchronized_pool_resource(const pool_options& __opts, memory_resource* __upstream)
       : __unsync_(__opts, __upstream) {}
diff --git a/libcxx/include/__memory_resource/unsynchronized_pool_resource.h b/libcxx/include/__memory_resource/unsynchronized_pool_resource.h
--- a/libcxx/include/__memory_resource/unsynchronized_pool_resource.h
+++ b/libcxx/include/__memory_resource/unsynchronized_pool_resource.h
@@ -27,7 +27,7 @@
 
 // [mem.res.pool.overview]
 
-class _LIBCPP_TYPE_VIS unsynchronized_pool_resource : public memory_resource {
+class _LIBCPP_TYPE_VIS _LIBCPP_AVAILABILITY_MEMORY_RESOURCE unsynchronized_pool_resource : public memory_resource {
   class __fixed_pool;
 
   class __adhoc_pool {
diff --git a/libcxx/test/libcxx/mem/mem.res/availability.verify.cpp b/libcxx/test/libcxx/mem/mem.res/availability.verify.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/libcxx/mem/mem.res/availability.verify.cpp
@@ -0,0 +1,24 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14
+// REQUIRES: use_system_cxx_lib && (target={{.+}}-apple-macosx10.{{9|10|11|12|13|14|15}} || target={{.+}}-apple-macosx{{11.0|12.0}})
+
+#include <memory_resource>
+
+void f() {
+  [[maybe_unused]] std::pmr::polymorphic_allocator<int> poly; // expected-error {{is unavailable}}
+  [[maybe_unused]] std::pmr::memory_resource* res;            // expected-error {{is unavailable}}
+  [[maybe_unused]] std::pmr::synchronized_pool_resource r1;   // expected-error {{is unavailable}}
+  [[maybe_unused]] std::pmr::monotonic_buffer_resource r2;    // expected-error {{is unavailable}}
+  [[maybe_unused]] std::pmr::unsynchronized_pool_resource r3; // expected-error {{is unavailable}}
+  (void)std::pmr::get_default_resource();                     // expected-error {{is unavailable}}
+  (void)std::pmr::set_default_resource(nullptr);              // expected-error {{is unavailable}}
+  (void)std::pmr::new_delete_resource();                      // expected-error {{is unavailable}}
+  (void)std::pmr::null_memory_resource();                     // expected-error {{is unavailable}}
+}