diff --git a/libcxx/docs/Cxx2aStatusPaperStatus.csv b/libcxx/docs/Cxx2aStatusPaperStatus.csv
--- a/libcxx/docs/Cxx2aStatusPaperStatus.csv
+++ b/libcxx/docs/Cxx2aStatusPaperStatus.csv
@@ -133,7 +133,7 @@
 "`P1661 <https://wg21.link/P1661>`__","LWG","Remove dedicated precalculated hash lookup interface","Cologne","|Nothing To Do|",""
 "`P1754 <https://wg21.link/P1754>`__","LWG","Rename concepts to standard_case for C++20, while we still can","Cologne","|In Progress|",""
 "","","","","",""
-"`P0883 <https://wg21.link/P0883>`__","LWG","Fixing Atomic Initialization","Belfast","* *",""
+"`P0883 <https://wg21.link/P0883>`__","LWG","Fixing Atomic Initialization","Belfast","|Complete|","13.0"
 "`P1391 <https://wg21.link/P1391>`__","LWG","Range constructor for std::string_view","Belfast","* *",""
 "`P1394 <https://wg21.link/P1394>`__","LWG","Range constructor for std::span","Belfast","* *",""
 "`P1456 <https://wg21.link/P1456>`__","LWG","Move-only views","Belfast","* *",""
diff --git a/libcxx/include/atomic b/libcxx/include/atomic
--- a/libcxx/include/atomic
+++ b/libcxx/include/atomic
@@ -67,7 +67,8 @@
     bool is_lock_free() const volatile noexcept;
     bool is_lock_free() const noexcept;
 
-    atomic() noexcept = default;
+    atomic() noexcept = default; // until C++20
+    constexpr atomic() noexcept(is_nothrow_default_constructible_v<T>); // since C++20
     constexpr atomic(T desr) noexcept;
     atomic(const atomic&) = delete;
     atomic& operator=(const atomic&) = delete;
@@ -201,7 +202,8 @@
     bool is_lock_free() const volatile noexcept;
     bool is_lock_free() const noexcept;
 
-    atomic() noexcept = default;
+    atomic() noexcept = default; // until C++17
+    constexpr atomic() noexcept; // since C++17
     constexpr atomic(T* desr) noexcept;
     atomic(const atomic&) = delete;
     atomic& operator=(const atomic&) = delete;
@@ -509,7 +511,8 @@
 
 typedef struct atomic_flag
 {
-    atomic_flag() noexcept = default;
+    atomic_flag() noexcept = default; // until C++17
+    constexpr atomic_flag() noexcept; // since C++20
     atomic_flag(const atomic_flag&) = delete;
     atomic_flag& operator=(const atomic_flag&) = delete;
     atomic_flag& operator=(const atomic_flag&) volatile = delete;
@@ -1673,8 +1676,13 @@
     _LIBCPP_AVAILABILITY_SYNC _LIBCPP_INLINE_VISIBILITY void notify_all() _NOEXCEPT
         {__cxx_atomic_notify_all(&__a_);}
 
+#if _LIBCPP_STD_VER >= 20
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+    __atomic_base() _NOEXCEPT : __a_{} {}
+#else
     _LIBCPP_INLINE_VISIBILITY
     __atomic_base() _NOEXCEPT _LIBCPP_DEFAULT
+#endif
 
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
     __atomic_base(_Tp __d) _NOEXCEPT : __a_(__d) {}
@@ -1700,8 +1708,15 @@
     : public __atomic_base<_Tp, false>
 {
     typedef __atomic_base<_Tp, false> __base;
+
+#if _LIBCPP_STD_VER >= 20
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+    __atomic_base() _NOEXCEPT : __base{} {}
+#else
     _LIBCPP_INLINE_VISIBILITY
     __atomic_base() _NOEXCEPT _LIBCPP_DEFAULT
+#endif
+
     _LIBCPP_INLINE_VISIBILITY
     _LIBCPP_CONSTEXPR __atomic_base(_Tp __d) _NOEXCEPT : __base(__d) {}
 
@@ -1783,8 +1798,15 @@
     typedef __atomic_base<_Tp> __base;
     typedef _Tp value_type;
     typedef value_type difference_type;
+
+#if _LIBCPP_STD_VER >= 20
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+    atomic() _NOEXCEPT_(is_nothrow_default_constructible_v<_Tp>) : __base{} {}
+#else
     _LIBCPP_INLINE_VISIBILITY
     atomic() _NOEXCEPT _LIBCPP_DEFAULT
+#endif
+
     _LIBCPP_INLINE_VISIBILITY
     _LIBCPP_CONSTEXPR atomic(_Tp __d) _NOEXCEPT : __base(__d) {}
 
@@ -1808,8 +1830,15 @@
     typedef __atomic_base<_Tp*> __base;
     typedef _Tp* value_type;
     typedef ptrdiff_t difference_type;
+
+#if _LIBCPP_STD_VER >= 20
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+    atomic() _NOEXCEPT : __base{} {}
+#else
     _LIBCPP_INLINE_VISIBILITY
     atomic() _NOEXCEPT _LIBCPP_DEFAULT
+#endif
+
     _LIBCPP_INLINE_VISIBILITY
     _LIBCPP_CONSTEXPR atomic(_Tp* __d) _NOEXCEPT : __base(__d) {}
 
@@ -2534,8 +2563,13 @@
     void notify_all() _NOEXCEPT
         {__cxx_atomic_notify_all(&__a_);}
 
+#if _LIBCPP_STD_VER >= 20
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+    atomic_flag() _NOEXCEPT : __a_{} {}
+#else
     _LIBCPP_INLINE_VISIBILITY
     atomic_flag() _NOEXCEPT _LIBCPP_DEFAULT
+#endif
 
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
     atomic_flag(bool __b) _NOEXCEPT : __a_(__b) {} // EXTENSION
diff --git a/libcxx/test/std/atomics/atomics.types.generic/constexpr_noexcept.pass.cpp b/libcxx/test/std/atomics/atomics.types.generic/constexpr_noexcept.pass.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/std/atomics/atomics.types.generic/constexpr_noexcept.pass.cpp
@@ -0,0 +1,35 @@
+//===----------------------------------------------------------------------===//
+//
+// 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, c++17
+// UNSUPPORTED: libcpp-has-no-threads
+
+#include <atomic>
+
+template <typename T>
+constexpr void test() {
+  [[maybe_unused]] constexpr T a;
+  static_assert(std::is_nothrow_constructible_v<T>);
+}
+
+struct throwing {
+  throwing();
+};
+
+struct trivial {
+  int a;
+};
+
+int main() {
+  test<std::atomic<int> >();
+  test<std::atomic<int*> >();
+  test<std::atomic<trivial> >();
+  test<std::atomic_flag>();
+
+  static_assert(!std::is_nothrow_constructible_v<std::atomic<throwing> >);
+}