diff --git a/libcxx/include/__availability b/libcxx/include/__availability
--- a/libcxx/include/__availability
+++ b/libcxx/include/__availability
@@ -138,6 +138,13 @@
 // #   define _LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_latch
 // #   define _LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_semaphore
 
+    // This controls the availability of the C++20 format library.
+    // The library is in development and not ABI stable yet. Currently
+    // P2216 is aiming to be retroactively accepted in C++20. This paper
+    // contains ABI breaking changes.
+#   define _LIBCPP_AVAILABILITY_FORMAT
+// #   define _LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_format
+
 #elif defined(__APPLE__)
 
 #   define _LIBCPP_AVAILABILITY_SHARED_MUTEX                                    \
@@ -223,6 +230,13 @@
 #   define _LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_latch
 #   define _LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_semaphore
 
+    // This controls the availability of the C++20 format library.
+    // The library is in development and not ABI stable yet. Currently
+    // P2216 is aiming to be retroactively accepted in C++20. This paper
+    // contains ABI breaking changes.
+#   define _LIBCPP_AVAILABILITY_FORMAT                                          \
+        __attribute__((unavailable))
+#   define _LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_format
 #else
 
 // ...New vendors can add availability markup here...
diff --git a/libcxx/include/__format/format_parse_context.h b/libcxx/include/__format/format_parse_context.h
--- a/libcxx/include/__format/format_parse_context.h
+++ b/libcxx/include/__format/format_parse_context.h
@@ -33,7 +33,7 @@
     !defined(_LIBCPP_HAS_NO_BUILTIN_IS_CONSTANT_EVALUATED)
 
 template <class _CharT>
-class _LIBCPP_TEMPLATE_VIS basic_format_parse_context {
+class _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FORMAT basic_format_parse_context {
 public:
   using char_type = _CharT;
   using const_iterator = typename basic_string_view<_CharT>::const_iterator;
diff --git a/libcxx/include/version b/libcxx/include/version
--- a/libcxx/include/version
+++ b/libcxx/include/version
@@ -319,7 +319,9 @@
 # define __cpp_lib_erase_if                             202002L
 # undef  __cpp_lib_execution
 // # define __cpp_lib_execution                            201902L
-// # define __cpp_lib_format                               201907L
+# if !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_format)
+// #   define __cpp_lib_format                             201907L
+# endif
 # define __cpp_lib_generic_unordered_lookup             201811L
 # define __cpp_lib_int_pow2                             202002L
 # if !defined(_LIBCPP_HAS_NO_CONCEPTS)
diff --git a/libcxx/utils/generate_feature_test_macro_components.py b/libcxx/utils/generate_feature_test_macro_components.py
--- a/libcxx/utils/generate_feature_test_macro_components.py
+++ b/libcxx/utils/generate_feature_test_macro_components.py
@@ -300,6 +300,8 @@
     "name": "__cpp_lib_format",
     "values": { "c++20": 201907 },
     "headers": ["format"],
+    "test_suite_guard": "!defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_format)",
+    "libcxx_guard": "!defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_format)",
     "unimplemented": True,
   }, {
     "name": "__cpp_lib_gcd_lcm",