Index: libcxx/docs/FeatureTestMacroTable.rst
===================================================================
--- libcxx/docs/FeatureTestMacroTable.rst
+++ libcxx/docs/FeatureTestMacroTable.rst
@@ -196,6 +196,8 @@
     ------------------------------------------------- -----------------
     ``__cpp_lib_list_remove_return_type``             ``201806L``      
     ------------------------------------------------- -----------------
+    ``__cpp_lib_math_constants``                      ``201907L``      
+    ------------------------------------------------- -----------------
     ``__cpp_lib_ranges``                              *unimplemented*  
     ------------------------------------------------- -----------------
     ``__cpp_lib_three_way_comparison``                *unimplemented*  
Index: libcxx/include/CMakeLists.txt
===================================================================
--- libcxx/include/CMakeLists.txt
+++ libcxx/include/CMakeLists.txt
@@ -118,6 +118,7 @@
   mutex
   new
   numeric
+  numbers
   optional
   ostream
   queue
Index: libcxx/include/module.modulemap
===================================================================
--- libcxx/include/module.modulemap
+++ libcxx/include/module.modulemap
@@ -382,6 +382,10 @@
     header "numeric"
     export *
   }
+  module numbers {
+    header "numbers"
+    export *
+  }
   module optional {
     header "optional"
     export *
Index: libcxx/include/numbers
===================================================================
--- /dev/null
+++ libcxx/include/numbers
@@ -0,0 +1,232 @@
+// -*- C++ -*-
+//===---------------------------- numbers ---------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_NUMBERS
+#define _LIBCPP_NUMBERS
+
+/*
+    numbers synopsis
+
+namespace std::numbers
+{
+  template<class T> inline constexpr T e_v          = unspecified;
+  template<class T> inline constexpr T log2e_v      = unspecified;
+  template<class T> inline constexpr T log10e_v     = unspecified;
+  template<class T> inline constexpr T pi_v         = unspecified;
+  template<class T> inline constexpr T inv_pi_v     = unspecified;
+  template<class T> inline constexpr T inv_sqrtpi_v = unspecified;
+  template<class T> inline constexpr T ln2_v        = unspecified;
+  template<class T> inline constexpr T ln10_v       = unspecified;
+  template<class T> inline constexpr T sqrt2_v      = unspecified;
+  template<class T> inline constexpr T sqrt3_v      = unspecified;
+  template<class T> inline constexpr T inv_sqrt3_v  = unspecified;
+  template<class T> inline constexpr T egamma_v     = unspecified;
+  template<class T> inline constexpr T phi_v        = unspecified;
+
+  template<floating_point T> inline constexpr T e_v<T>          = see below;
+  template<floating_point T> inline constexpr T log2e_v<T>      = see below;
+  template<floating_point T> inline constexpr T log10e_v<T>     = see below;
+  template<floating_point T> inline constexpr T pi_v<T>         = see below;
+  template<floating_point T> inline constexpr T inv_pi_v<T>     = see below;
+  template<floating_point T> inline constexpr T inv_sqrtpi_v<T> = see below;
+  template<floating_point T> inline constexpr T ln2_v<T>        = see below;
+  template<floating_point T> inline constexpr T ln10_v<T>       = see below;
+  template<floating_point T> inline constexpr T sqrt2_v<T>      = see below;
+  template<floating_point T> inline constexpr T sqrt3_v<T>      = see below;
+  template<floating_point T> inline constexpr T inv_sqrt3_v<T>  = see below;
+  template<floating_point T> inline constexpr T egamma_v<T>     = see below;
+  template<floating_point T> inline constexpr T phi_v<T>        = see below;
+
+  inline constexpr double e          = e_v<double>;
+  inline constexpr double log2e      = log2e_v<double>;
+  inline constexpr double log10e     = log10e_v<double>;
+  inline constexpr double pi         = pi_v<double>;
+  inline constexpr double inv_pi     = inv_pi_v<double>;
+  inline constexpr double inv_sqrtpi = inv_sqrtpi_v<double>;
+  inline constexpr double ln2        = ln2_v<double>;
+  inline constexpr double ln10       = ln10_v<double>;
+  inline constexpr double sqrt2      = sqrt2_v<double>;
+  inline constexpr double sqrt3      = sqrt3_v<double>;
+  inline constexpr double inv_sqrt3  = inv_sqrt3_v<double>;
+  inline constexpr double egamma     = egamma_v<double>;
+  inline constexpr double phi        = phi_v<double>;
+}  // std::numbers
+
+*/
+
+#include <__config>
+#include <type_traits>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER > 17
+
+namespace numbers {
+
+template<class>
+inline constexpr bool value = false;
+
+template<class T>
+constexpr T _AlwaysFalse() {
+   static_assert(value<T>, "Require Floating Point types");
+   return T();
+}
+
+template<class T>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+                   T e_v             = _AlwaysFalse<T>();
+template<class T>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+                   T log2e_v         = _AlwaysFalse<T>();
+template<class T>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+                   T log10e_v        = _AlwaysFalse<T>();
+template<class T>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+                   T pi_v            = _AlwaysFalse<T>();
+template<class T>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+                   T inv_pi_v        = _AlwaysFalse<T>();
+template<class T>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+                   T inv_sqrtpi_v    = _AlwaysFalse<T>();
+template<class T>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+                   T ln2_v           = _AlwaysFalse<T>();
+template<class T>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+                   T ln10_v          = _AlwaysFalse<T>();
+template<class T>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+                   T sqrt2_v         = _AlwaysFalse<T>();
+template<class T>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+                   T sqrt3_v         = _AlwaysFalse<T>();
+template<class T>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+                   T inv_sqrt3_v     = _AlwaysFalse<T>();
+template<class T>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+                   T egamma_v        = _AlwaysFalse<T>();
+template<class T>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+                   T phi_v           = _AlwaysFalse<T>();
+
+template<typename T>
+concept floating_point = is_floating_point_v<T>;
+
+// e
+template<floating_point T>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+T e_v<T> = T(2.718281828459045235360287471352662498L);
+
+// log2(e)
+template<floating_point T>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+T log2e_v<T> = T(1.442695040888963407359924681001892137L);
+
+// log10(e)
+template<floating_point T>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+T log10e_v<T> = T(0.434294481903251827651128918916605082L);
+
+// pi
+template<floating_point T>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+T pi_v<T> = T(3.141592653589793238462643383279502884L);
+
+// 1/pi
+template<floating_point T>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+T inv_pi_v<T> = T(0.318309886183790671537767526745028724L);
+
+// 1/sqrt(pi)
+template<floating_point T>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+T inv_sqrtpi_v<T> = T(0.564189583547756286948079451560772586L);
+
+// log_e(2)
+template<floating_point T>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+T ln2_v<T> = T(0.693147180559945309417232121458176568L);
+
+// log_e(10)
+template<floating_point T>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+T ln10_v<T> = T(2.302585092994045684017991454684364208L);
+
+// sqrt(2)
+template<floating_point T>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+T sqrt2_v<T> = T(1.414213562373095048801688724209698078L);
+
+// sqrt(3)
+template<floating_point T>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+T sqrt3_v<T> = T(1.732050807568877293527446341505872366L);
+
+// 1/sqrt(3)
+template<floating_point T>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+T inv_sqrt3_v<T> = T(0.577350269189625764509148780501957456L);
+
+// Euler-Mascheroni gama constant
+template<floating_point T>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+T egamma_v<T> = T(0.577215664901532860606512090082402402431L);
+
+// Golden ratio phi constant
+template<floating_point T>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+T phi_v<T> = T(1.618033988749894848204586834365638117L);
+
+
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+                   double e          = e_v<double>;
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+                   double log2e      = log2e_v<double>;
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+                   double log10e     = log10e_v<double>;
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+                   double pi         = pi_v<double>;
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+                   double inv_pi     = inv_pi_v<double>;
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+                   double inv_sqrtpi = inv_sqrtpi_v<double>;
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+                   double ln2        = ln2_v<double>;
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+                   double ln10       = ln10_v<double>;
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+                   double sqrt2      = sqrt2_v<double>;
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+                   double sqrt3      = sqrt3_v<double>;
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+                   double inv_sqrt3  = inv_sqrt3_v<double>;
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+                   double egamma     = egamma_v<double>;
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR
+                   double phi        = phi_v<double>;
+
+} //namespace numbers
+
+#endif //_LIBCPP_STD_VER > 17
+
+_LIBCPP_END_NAMESPACE_STD
+
+_LIBCPP_POP_MACROS
+
+#endif  //_LIBCPP_NUMBERS
Index: libcxx/include/version
===================================================================
--- libcxx/include/version
+++ libcxx/include/version
@@ -74,6 +74,7 @@
 __cpp_lib_make_reverse_iterator                         201402L <iterator>
 __cpp_lib_make_unique                                   201304L <memory>
 __cpp_lib_map_try_emplace                               201411L <map>
+__cpp_lib_math_constants                                201907L <numbers>
 __cpp_lib_math_special_functions                        201603L <cmath>
 __cpp_lib_memory_resource                               201603L <memory_resource>
 __cpp_lib_node_extract                                  201606L <map> <set> <unordered_map>
@@ -233,9 +234,10 @@
 #   define __cpp_lib_is_constant_evaluated              201811L
 # endif
 # define __cpp_lib_list_remove_return_type              201806L
+# define __cpp_lib_math_constants                       201907L
 // # define __cpp_lib_ranges                               201811L
-# define __cpp_lib_to_array                                201907L
 // # define __cpp_lib_three_way_comparison                 201711L
+# define __cpp_lib_to_array                             201907L
 #endif
 
 #endif // _LIBCPP_VERSIONH
Index: libcxx/test/libcxx/double_include.sh.cpp
===================================================================
--- libcxx/test/libcxx/double_include.sh.cpp
+++ libcxx/test/libcxx/double_include.sh.cpp
@@ -99,6 +99,7 @@
 #endif
 #include <new>
 #include <numeric>
+#include <numbers>
 #include <optional>
 #include <ostream>
 #include <queue>
Index: libcxx/test/std/language.support/support.limits/support.limits.general/numbers.version.pass.cpp
===================================================================
--- /dev/null
+++ libcxx/test/std/language.support/support.limits/support.limits.general/numbers.version.pass.cpp
@@ -0,0 +1,52 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// WARNING: This test was generated by generate_feature_test_macro_components.py
+// and should not be edited manually.
+
+// <numbers>
+
+// Test the feature test macros defined by <numbers>
+
+/*  Constant                    Value
+    __cpp_lib_math_constants    201907L [C++2a]
+*/
+
+#include <numbers>
+#include "test_macros.h"
+
+#if TEST_STD_VER < 14
+
+# ifdef __cpp_lib_math_constants
+#   error "__cpp_lib_math_constants should not be defined before c++2a"
+# endif
+
+#elif TEST_STD_VER == 14
+
+# ifdef __cpp_lib_math_constants
+#   error "__cpp_lib_math_constants should not be defined before c++2a"
+# endif
+
+#elif TEST_STD_VER == 17
+
+# ifdef __cpp_lib_math_constants
+#   error "__cpp_lib_math_constants should not be defined before c++2a"
+# endif
+
+#elif TEST_STD_VER > 17
+
+# ifndef __cpp_lib_math_constants
+#   error "__cpp_lib_math_constants should be defined in c++2a"
+# endif
+# if __cpp_lib_math_constants != 201907L
+#   error "__cpp_lib_math_constants should have the value 201907L in c++2a"
+# endif
+
+#endif // TEST_STD_VER > 17
+
+int main(int, char**) { return 0; }
Index: libcxx/test/std/language.support/support.limits/support.limits.general/version.version.pass.cpp
===================================================================
--- libcxx/test/std/language.support/support.limits/support.limits.general/version.version.pass.cpp
+++ libcxx/test/std/language.support/support.limits/support.limits.general/version.version.pass.cpp
@@ -66,6 +66,7 @@
     __cpp_lib_make_reverse_iterator                201402L [C++14]
     __cpp_lib_make_unique                          201304L [C++14]
     __cpp_lib_map_try_emplace                      201411L [C++17]
+    __cpp_lib_math_constants                       201907L [C++2a]
     __cpp_lib_math_special_functions               201603L [C++17]
     __cpp_lib_memory_resource                      201603L [C++17]
     __cpp_lib_node_extract                         201606L [C++17]
@@ -315,6 +316,10 @@
 #   error "__cpp_lib_map_try_emplace should not be defined before c++17"
 # endif
 
+# ifdef __cpp_lib_math_constants
+#   error "__cpp_lib_math_constants should not be defined before c++2a"
+# endif
+
 # ifdef __cpp_lib_math_special_functions
 #   error "__cpp_lib_math_special_functions should not be defined before c++17"
 # endif
@@ -687,6 +692,10 @@
 #   error "__cpp_lib_map_try_emplace should not be defined before c++17"
 # endif
 
+# ifdef __cpp_lib_math_constants
+#   error "__cpp_lib_math_constants should not be defined before c++2a"
+# endif
+
 # ifdef __cpp_lib_math_special_functions
 #   error "__cpp_lib_math_special_functions should not be defined before c++17"
 # endif
@@ -1215,6 +1224,10 @@
 #   error "__cpp_lib_map_try_emplace should have the value 201411L in c++17"
 # endif
 
+# ifdef __cpp_lib_math_constants
+#   error "__cpp_lib_math_constants should not be defined before c++2a"
+# endif
+
 # if !defined(_LIBCPP_VERSION)
 #   ifndef __cpp_lib_math_special_functions
 #     error "__cpp_lib_math_special_functions should be defined in c++17"
@@ -1941,6 +1954,13 @@
 #   error "__cpp_lib_map_try_emplace should have the value 201411L in c++2a"
 # endif
 
+# ifndef __cpp_lib_math_constants
+#   error "__cpp_lib_math_constants should be defined in c++2a"
+# endif
+# if __cpp_lib_math_constants != 201907L
+#   error "__cpp_lib_math_constants should have the value 201907L in c++2a"
+# endif
+
 # if !defined(_LIBCPP_VERSION)
 #   ifndef __cpp_lib_math_special_functions
 #     error "__cpp_lib_math_special_functions should be defined in c++2a"
Index: libcxx/test/std/numerics/numbers/numbers.fail.cpp
===================================================================
--- /dev/null
+++ libcxx/test/std/numerics/numbers/numbers.fail.cpp
@@ -0,0 +1,22 @@
+//===----------------------------------------------------------------------===//
+//
+// 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++98, c++03, c++11, c++14, c++17
+
+
+#include<numbers>
+#include "test_macros.h"
+struct S1 {
+};
+int main(){
+
+  constexpr int d = std::numbers::e_v<int>; // expected-error-re@numbers:* {{static_assert failed{{( due to requirement '.*')?}}}}
+  constexpr S1 s  = std::numbers::e_v<S1>;  // expected-error-re@numbers:* {{static_assert failed{{( due to requirement '.*')?}}}}
+    return 0;
+}
+
Index: libcxx/test/std/numerics/numbers/numbers.pass.cpp
===================================================================
--- /dev/null
+++ libcxx/test/std/numerics/numbers/numbers.pass.cpp
@@ -0,0 +1,79 @@
+//===----------------------------------------------------------------------===//
+//
+// 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++98, c++03, c++11, c++14, c++17
+
+
+#include <numbers>
+#include "test_macros.h"
+
+int main() {
+
+  // float
+  constexpr float f   = std::numbers::e_v<float>;
+  constexpr float f1  = std::numbers::log2e_v<float>;
+  constexpr float f2  = std::numbers::log10e_v<float>;
+  constexpr float f3  = std::numbers::pi_v<float>;
+  constexpr float f4  = std::numbers::inv_pi_v<float>;
+  constexpr float f5  = std::numbers::inv_sqrtpi_v<float>;
+  constexpr float f6  = std::numbers::ln2_v<float>;
+  constexpr float f7  = std::numbers::ln10_v<float>;
+  constexpr float f8  = std::numbers::sqrt2_v<float>;
+  constexpr float f9  = std::numbers::sqrt3_v<float>;
+  constexpr float f10 = std::numbers::inv_sqrt3_v<float>;
+  constexpr float f11 = std::numbers::egamma_v<float>;
+  constexpr float f12 = std::numbers::phi_v<float>;
+
+  // double
+  constexpr double d   = std::numbers::e_v<double>;
+  constexpr double d1  = std::numbers::log2e_v<double>;
+  constexpr double d2  = std::numbers::log10e_v<double>;
+  constexpr double d3  = std::numbers::pi_v<double>;
+  constexpr double d4  = std::numbers::inv_pi_v<double>;
+  constexpr double d5  = std::numbers::inv_sqrtpi_v<double>;
+  constexpr double d6  = std::numbers::ln2_v<double>;
+  constexpr double d7  = std::numbers::ln10_v<double>;
+  constexpr double d8  = std::numbers::sqrt2_v<double>;
+  constexpr double d9  = std::numbers::sqrt3_v<double>;
+  constexpr double d10 = std::numbers::inv_sqrt3_v<double>;
+  constexpr double d11 = std::numbers::egamma_v<double>;
+  constexpr double d12 = std::numbers::phi_v<double>;
+  // static assert checks
+  static_assert(d == std::numbers::e, "d != std::numbers::e ");
+  static_assert(d1 == std::numbers::log2e, "d1 != std::numbers::log2e");
+  static_assert(d2 == std::numbers::log10e, "d2 != std::numbers::log10e");
+  static_assert(d3 == std::numbers::pi, "d3 != std::numbers::pi");
+  static_assert(d4 == std::numbers::inv_pi, "d4 != std::numbers::inv_pi");
+  static_assert(d5 == std::numbers::inv_sqrtpi, "d5 != std::numbers::inv_sqrtpi");
+  static_assert(d6 == std::numbers::ln2, "d6 != std::numbers::ln2");
+  static_assert(d7 == std::numbers::ln10, "d7 != std::numbers::ln10");
+  static_assert(d8 == std::numbers::sqrt2, "d8 != std::numbers::sqrt2");
+  static_assert(d9 == std::numbers::sqrt3, "d9 != std::numbers::sqrt3");
+  static_assert(d10 == std::numbers::inv_sqrt3, "d10 != std::numbers::inv_sqrt3");
+  static_assert(d11 == std::numbers::egamma, "d11 != std::numbers::egamma");
+  static_assert(d12 == std::numbers::phi, "d12 != std::numbers::phi");
+  // long oduble
+  constexpr long double ld   = std::numbers::e_v<long double>;
+  constexpr long double ld1  = std::numbers::log2e_v<long double>;
+  constexpr long double ld2  = std::numbers::log10e_v<long double>;
+  constexpr long double ld3  = std::numbers::pi_v<long double>;
+  constexpr long double ld4  = std::numbers::inv_pi_v<long double>;
+  constexpr long double ld5  = std::numbers::inv_sqrtpi_v<long double>;
+  constexpr long double ld6  = std::numbers::ln2_v<long double>;
+  constexpr long double ld7  = std::numbers::ln10_v<long double>;
+  constexpr long double ld8  = std::numbers::sqrt2_v<long double>;
+  constexpr long double ld9  = std::numbers::sqrt3_v<long double>;
+  constexpr long double ld10 = std::numbers::inv_sqrt3_v<long double>;
+  constexpr long double ld11 = std::numbers::egamma_v<long double>;
+  constexpr long double ld12 = std::numbers::phi_v<long double>;
+
+  return 0;
+
+}
+
+
Index: libcxx/utils/generate_feature_test_macro_components.py
===================================================================
--- libcxx/utils/generate_feature_test_macro_components.py
+++ libcxx/utils/generate_feature_test_macro_components.py
@@ -591,6 +591,12 @@
    },
    "headers": ["array"],
    },
+  {"name": "__cpp_lib_math_constants",
+   "values": {
+     "c++2a": 201907L,
+   },
+   "headers": ["numbers"],
+   },
 ]], key=lambda tc: tc["name"])
 
 def get_std_dialects():