diff --git a/libcxx/include/__config b/libcxx/include/__config
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -1253,10 +1253,12 @@
 #   define _LIBCPP_THREAD_SAFETY_ANNOTATION(x)
 #endif
 
-#if __has_attribute(require_constant_initialization)
-#  define _LIBCPP_SAFE_STATIC __attribute__((__require_constant_initialization__))
+#if _LIBCPP_STD_VER > 17
+#  define _LIBCPP_CONSTINIT constinit
+#elif __has_attribute(require_constant_initialization)
+#  define _LIBCPP_CONSTINIT __attribute__((__require_constant_initialization__))
 #else
-#  define _LIBCPP_SAFE_STATIC
+#  define _LIBCPP_CONSTINIT
 #endif
 
 #if __has_attribute(diagnose_if) && !defined(_LIBCPP_DISABLE_ADDITIONAL_DIAGNOSTICS)
diff --git a/libcxx/src/debug.cpp b/libcxx/src/debug.cpp
--- a/libcxx/src/debug.cpp
+++ b/libcxx/src/debug.cpp
@@ -35,7 +35,7 @@
     std::abort();
 }
 
-_LIBCPP_SAFE_STATIC __libcpp_debug_function_type
+_LIBCPP_CONSTINIT __libcpp_debug_function_type
     __libcpp_debug_function = __libcpp_abort_debug_function;
 
 bool __libcpp_set_debug_function(__libcpp_debug_function_type __func) {
diff --git a/libcxx/src/experimental/memory_resource.cpp b/libcxx/src/experimental/memory_resource.cpp
--- a/libcxx/src/experimental/memory_resource.cpp
+++ b/libcxx/src/experimental/memory_resource.cpp
@@ -97,7 +97,7 @@
 __default_memory_resource(bool set = false, memory_resource * new_res = nullptr) noexcept
 {
 #ifndef _LIBCPP_HAS_NO_ATOMIC_HEADER
-    _LIBCPP_SAFE_STATIC static atomic<memory_resource*> __res{&res_init.resources.new_delete_res};
+    static _LIBCPP_CONSTINIT atomic<memory_resource*> __res{&res_init.resources.new_delete_res};
     if (set) {
         new_res = new_res ? new_res : new_delete_resource();
         // TODO: Can a weaker ordering be used?
@@ -109,7 +109,7 @@
             &__res, memory_order_acquire);
     }
 #elif !defined(_LIBCPP_HAS_NO_THREADS)
-    _LIBCPP_SAFE_STATIC static memory_resource * res = &res_init.resources.new_delete_res;
+    static _LIBCPP_CONSTINIT memory_resource *res = &res_init.resources.new_delete_res;
     static mutex res_lock;
     if (set) {
         new_res = new_res ? new_res : new_delete_resource();
@@ -122,7 +122,7 @@
         return res;
     }
 #else
-    _LIBCPP_SAFE_STATIC static memory_resource* res = &res_init.resources.new_delete_res;
+    static _LIBCPP_CONSTINIT memory_resource *res = &res_init.resources.new_delete_res;
     if (set) {
         new_res = new_res ? new_res : new_delete_resource();
         memory_resource * old_res = res;
diff --git a/libcxx/src/experimental/memory_resource_init_helper.h b/libcxx/src/experimental/memory_resource_init_helper.h
--- a/libcxx/src/experimental/memory_resource_init_helper.h
+++ b/libcxx/src/experimental/memory_resource_init_helper.h
@@ -1,2 +1,2 @@
 #pragma GCC system_header
-_LIBCPP_SAFE_STATIC ResourceInitHelper res_init _LIBCPP_INIT_PRIORITY_MAX;
+_LIBCPP_CONSTINIT ResourceInitHelper res_init _LIBCPP_INIT_PRIORITY_MAX;
diff --git a/libcxx/src/memory.cpp b/libcxx/src/memory.cpp
--- a/libcxx/src/memory.cpp
+++ b/libcxx/src/memory.cpp
@@ -132,8 +132,8 @@
 
 #if !defined(_LIBCPP_HAS_NO_THREADS)
 
-_LIBCPP_SAFE_STATIC static const std::size_t __sp_mut_count = 16;
-_LIBCPP_SAFE_STATIC static __libcpp_mutex_t mut_back[__sp_mut_count] =
+static constexpr std::size_t __sp_mut_count = 16;
+static _LIBCPP_CONSTINIT __libcpp_mutex_t mut_back[__sp_mut_count] =
 {
     _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER,
     _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER,
@@ -171,8 +171,7 @@
 __sp_mut&
 __get_sp_mut(const void* p)
 {
-    static __sp_mut muts[__sp_mut_count]
-    {
+    static _LIBCPP_CONSTINIT __sp_mut muts[__sp_mut_count] = {
         &mut_back[ 0], &mut_back[ 1], &mut_back[ 2], &mut_back[ 3],
         &mut_back[ 4], &mut_back[ 5], &mut_back[ 6], &mut_back[ 7],
         &mut_back[ 8], &mut_back[ 9], &mut_back[10], &mut_back[11],
diff --git a/libcxx/src/mutex.cpp b/libcxx/src/mutex.cpp
--- a/libcxx/src/mutex.cpp
+++ b/libcxx/src/mutex.cpp
@@ -196,8 +196,8 @@
 // keep in sync with:  7741191.
 
 #ifndef _LIBCPP_HAS_NO_THREADS
-_LIBCPP_SAFE_STATIC static __libcpp_mutex_t mut = _LIBCPP_MUTEX_INITIALIZER;
-_LIBCPP_SAFE_STATIC static __libcpp_condvar_t cv = _LIBCPP_CONDVAR_INITIALIZER;
+static _LIBCPP_CONSTINIT __libcpp_mutex_t mut = _LIBCPP_MUTEX_INITIALIZER;
+static _LIBCPP_CONSTINIT __libcpp_condvar_t cv = _LIBCPP_CONDVAR_INITIALIZER;
 #endif
 
 void __call_once(volatile once_flag::_State_type& flag, void* arg,
diff --git a/libcxx/src/random_shuffle.cpp b/libcxx/src/random_shuffle.cpp
--- a/libcxx/src/random_shuffle.cpp
+++ b/libcxx/src/random_shuffle.cpp
@@ -18,7 +18,7 @@
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #ifndef _LIBCPP_HAS_NO_THREADS
-_LIBCPP_SAFE_STATIC static __libcpp_mutex_t __rs_mut = _LIBCPP_MUTEX_INITIALIZER;
+static _LIBCPP_CONSTINIT __libcpp_mutex_t __rs_mut = _LIBCPP_MUTEX_INITIALIZER;
 #endif
 unsigned __rs_default::__c_ = 0;
 
diff --git a/libcxx/src/support/runtime/exception_fallback.ipp b/libcxx/src/support/runtime/exception_fallback.ipp
--- a/libcxx/src/support/runtime/exception_fallback.ipp
+++ b/libcxx/src/support/runtime/exception_fallback.ipp
@@ -11,9 +11,8 @@
 
 namespace std {
 
-_LIBCPP_SAFE_STATIC static std::terminate_handler  __terminate_handler;
-_LIBCPP_SAFE_STATIC static std::unexpected_handler __unexpected_handler;
-
+static _LIBCPP_CONSTINIT std::terminate_handler  __terminate_handler = nullptr;
+static _LIBCPP_CONSTINIT std::unexpected_handler __unexpected_handler = nullptr;
 
 // libcxxrt provides implementations of these functions itself.
 unexpected_handler
@@ -26,7 +25,6 @@
 get_unexpected() noexcept
 {
   return __libcpp_atomic_load(&__unexpected_handler);
-
 }
 
 _LIBCPP_NORETURN
diff --git a/libcxx/src/support/runtime/new_handler_fallback.ipp b/libcxx/src/support/runtime/new_handler_fallback.ipp
--- a/libcxx/src/support/runtime/new_handler_fallback.ipp
+++ b/libcxx/src/support/runtime/new_handler_fallback.ipp
@@ -9,7 +9,7 @@
 
 namespace std {
 
-_LIBCPP_SAFE_STATIC static std::new_handler __new_handler;
+static _LIBCPP_CONSTINIT std::new_handler __new_handler = nullptr;
 
 new_handler
 set_new_handler(new_handler handler) noexcept
diff --git a/libcxx/test/std/experimental/language.support/support.coroutines/coroutine.trivial.awaitables/suspend_always.pass.cpp b/libcxx/test/std/experimental/language.support/support.coroutines/coroutine.trivial.awaitables/suspend_always.pass.cpp
--- a/libcxx/test/std/experimental/language.support/support.coroutines/coroutine.trivial.awaitables/suspend_always.pass.cpp
+++ b/libcxx/test/std/experimental/language.support/support.coroutines/coroutine.trivial.awaitables/suspend_always.pass.cpp
@@ -18,8 +18,7 @@
 
 using SuspendT = std::experimental::coroutines_v1::suspend_always;
 
-TEST_SAFE_STATIC SuspendT safe_sa;
-constexpr SuspendT constexpr_sa;
+constexpr SuspendT constexpr_sa; // check constexpr-friendliness
 
 constexpr bool check_suspend_constexpr() {
   SuspendT s{};
diff --git a/libcxx/test/std/experimental/language.support/support.coroutines/coroutine.trivial.awaitables/suspend_never.pass.cpp b/libcxx/test/std/experimental/language.support/support.coroutines/coroutine.trivial.awaitables/suspend_never.pass.cpp
--- a/libcxx/test/std/experimental/language.support/support.coroutines/coroutine.trivial.awaitables/suspend_never.pass.cpp
+++ b/libcxx/test/std/experimental/language.support/support.coroutines/coroutine.trivial.awaitables/suspend_never.pass.cpp
@@ -19,8 +19,7 @@
 // Test that the type is in the correct namespace
 using SuspendT = std::experimental::coroutines_v1::suspend_never;
 
-TEST_SAFE_STATIC SuspendT safe_sn;
-constexpr SuspendT constexpr_sn;
+constexpr SuspendT constexpr_sn; // test constexpr-friendliness
 
 constexpr bool check_suspend_constexpr() {
   SuspendT s{};
diff --git a/libcxx/test/std/language.support/support.coroutines/coroutine.trivial.awaitables/suspend_always.pass.cpp b/libcxx/test/std/language.support/support.coroutines/coroutine.trivial.awaitables/suspend_always.pass.cpp
--- a/libcxx/test/std/language.support/support.coroutines/coroutine.trivial.awaitables/suspend_always.pass.cpp
+++ b/libcxx/test/std/language.support/support.coroutines/coroutine.trivial.awaitables/suspend_always.pass.cpp
@@ -16,8 +16,6 @@
 
 #include "test_macros.h"
 
-TEST_SAFE_STATIC std::suspend_always safe_sa;
-
 constexpr bool check_suspend_constexpr() {
   std::suspend_always s{};
   const std::suspend_always scopy(s);
diff --git a/libcxx/test/std/language.support/support.coroutines/coroutine.trivial.awaitables/suspend_never.pass.cpp b/libcxx/test/std/language.support/support.coroutines/coroutine.trivial.awaitables/suspend_never.pass.cpp
--- a/libcxx/test/std/language.support/support.coroutines/coroutine.trivial.awaitables/suspend_never.pass.cpp
+++ b/libcxx/test/std/language.support/support.coroutines/coroutine.trivial.awaitables/suspend_never.pass.cpp
@@ -16,11 +16,6 @@
 
 #include "test_macros.h"
 
-// Test that the type 'std::suspend_never' is in the correct namespace
-
-TEST_SAFE_STATIC std::suspend_never safe_sn;
-constexpr std::suspend_never constexpr_sn;
-
 constexpr bool check_suspend_constexpr() {
   std::suspend_never s{};
   const std::suspend_never scopy(s); ((void)scopy);
diff --git a/libcxx/test/std/utilities/any/any.class/any.cons/default.pass.cpp b/libcxx/test/std/utilities/any/any.class/any.cons/default.pass.cpp
--- a/libcxx/test/std/utilities/any/any.class/any.cons/default.pass.cpp
+++ b/libcxx/test/std/utilities/any/any.class/any.cons/default.pass.cpp
@@ -33,8 +33,8 @@
         struct TestConstexpr : public std::any {
           constexpr TestConstexpr() : std::any() {}
         };
-        TEST_SAFE_STATIC static std::any a;
-        ((void)a);
+        static TEST_CONSTINIT std::any a;
+        (void)a;
     }
     {
         DisableAllocationGuard g; ((void)g);
diff --git a/libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.class/unique.ptr.ctor/default.pass.cpp b/libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.class/unique.ptr.ctor/default.pass.cpp
--- a/libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.class/unique.ptr.ctor/default.pass.cpp
+++ b/libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.class/unique.ptr.ctor/default.pass.cpp
@@ -31,8 +31,8 @@
 #include "unique_ptr_test_helper.h"
 
 #if TEST_STD_VER >= 11
-TEST_SAFE_STATIC std::unique_ptr<int> global_static_unique_ptr_single;
-TEST_SAFE_STATIC std::unique_ptr<int[]> global_static_unique_ptr_runtime;
+TEST_CONSTINIT std::unique_ptr<int> global_static_unique_ptr_single;
+TEST_CONSTINIT std::unique_ptr<int[]> global_static_unique_ptr_runtime;
 
 struct NonDefaultDeleter {
   NonDefaultDeleter() = delete;
diff --git a/libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.class/unique.ptr.ctor/nullptr.pass.cpp b/libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.class/unique.ptr.ctor/nullptr.pass.cpp
--- a/libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.class/unique.ptr.ctor/nullptr.pass.cpp
+++ b/libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.class/unique.ptr.ctor/nullptr.pass.cpp
@@ -20,8 +20,8 @@
 
 
 #if TEST_STD_VER >= 11
-TEST_SAFE_STATIC std::unique_ptr<int> global_static_unique_ptr_single(nullptr);
-TEST_SAFE_STATIC std::unique_ptr<int[]> global_static_unique_ptr_runtime(nullptr);
+TEST_CONSTINIT std::unique_ptr<int> global_static_unique_ptr_single(nullptr);
+TEST_CONSTINIT std::unique_ptr<int[]> global_static_unique_ptr_runtime(nullptr);
 
 struct NonDefaultDeleter {
   NonDefaultDeleter() = delete;
diff --git a/libcxx/test/support/test_macros.h b/libcxx/test/support/test_macros.h
--- a/libcxx/test/support/test_macros.h
+++ b/libcxx/test/support/test_macros.h
@@ -206,10 +206,12 @@
 #define TEST_HAS_NO_ALIGNED_ALLOCATION
 #endif
 
-#if defined(_LIBCPP_SAFE_STATIC)
-#define TEST_SAFE_STATIC _LIBCPP_SAFE_STATIC
+#if TEST_STD_VER > 17
+#define TEST_CONSTINIT constinit
+#elif defined(_LIBCPP_CONSTINIT)
+#define TEST_CONSTINIT _LIBCPP_CONSTINIT
 #else
-#define TEST_SAFE_STATIC
+#define TEST_CONSTINIT
 #endif
 
 #if !defined(__cpp_impl_three_way_comparison) \
diff --git a/libcxxabi/src/cxa_default_handlers.cpp b/libcxxabi/src/cxa_default_handlers.cpp
--- a/libcxxabi/src/cxa_default_handlers.cpp
+++ b/libcxxabi/src/cxa_default_handlers.cpp
@@ -20,8 +20,7 @@
 
 #if !defined(LIBCXXABI_SILENT_TERMINATE)
 
-_LIBCPP_SAFE_STATIC
-static const char* cause = "uncaught";
+static _LIBCPP_CONSTINIT const char* cause = "uncaught";
 
 __attribute__((noreturn))
 static void demangling_terminate_handler()
@@ -100,13 +99,13 @@
 // Global variables that hold the pointers to the current handler
 //
 _LIBCXXABI_DATA_VIS
-_LIBCPP_SAFE_STATIC std::terminate_handler __cxa_terminate_handler = default_terminate_handler;
+_LIBCPP_CONSTINIT std::terminate_handler __cxa_terminate_handler = default_terminate_handler;
 
 _LIBCXXABI_DATA_VIS
-_LIBCPP_SAFE_STATIC std::unexpected_handler __cxa_unexpected_handler = default_unexpected_handler;
+_LIBCPP_CONSTINIT std::unexpected_handler __cxa_unexpected_handler = default_unexpected_handler;
 
 _LIBCXXABI_DATA_VIS
-_LIBCPP_SAFE_STATIC std::new_handler __cxa_new_handler = 0;
+_LIBCPP_CONSTINIT std::new_handler __cxa_new_handler = 0;
 
 namespace std
 {
diff --git a/libcxxabi/src/cxa_guard_impl.h b/libcxxabi/src/cxa_guard_impl.h
--- a/libcxxabi/src/cxa_guard_impl.h
+++ b/libcxxabi/src/cxa_guard_impl.h
@@ -619,7 +619,7 @@
   static T instance;
 };
 template <class T>
-_LIBCPP_SAFE_STATIC T GlobalStatic<T>::instance = {};
+_LIBCPP_CONSTINIT T GlobalStatic<T>::instance = {};
 
 enum class Implementation { NoThreads, GlobalMutex, Futex };
 
diff --git a/libcxxabi/src/fallback_malloc.cpp b/libcxxabi/src/fallback_malloc.cpp
--- a/libcxxabi/src/fallback_malloc.cpp
+++ b/libcxxabi/src/fallback_malloc.cpp
@@ -33,8 +33,7 @@
 
 // When POSIX threads are not available, make the mutex operations a nop
 #ifndef _LIBCXXABI_HAS_NO_THREADS
-_LIBCPP_SAFE_STATIC
-static std::__libcpp_mutex_t heap_mutex = _LIBCPP_MUTEX_INITIALIZER;
+static _LIBCPP_CONSTINIT std::__libcpp_mutex_t heap_mutex = _LIBCPP_MUTEX_INITIALIZER;
 #else
 static void* heap_mutex = 0;
 #endif