diff --git a/libcxx/docs/ReleaseNotes.rst b/libcxx/docs/ReleaseNotes.rst
--- a/libcxx/docs/ReleaseNotes.rst
+++ b/libcxx/docs/ReleaseNotes.rst
@@ -51,6 +51,12 @@
   has been shipping since LLVM 14, so the Coroutines TS implementation is being removed per our policy
   for removing TSes.
 
+- Several incidental transitive includes have been removed from libc++. Those
+  includes are removed based on the language version used. Incidental transitive
+  inclusions of the following headers have been removed:
+
+  - C++2b: ``cstring``
+
 Upcoming Deprecations and Removals
 ----------------------------------
 
diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -540,6 +540,7 @@
   __split_buffer
   __std_stream
   __string/char_traits.h
+  __string/constexpr_c_functions.h
   __string/extern_template_lists.h
   __support/android/locale_bionic.h
   __support/fuchsia/xlocale.h
diff --git a/libcxx/include/__bit_reference b/libcxx/include/__bit_reference
--- a/libcxx/include/__bit_reference
+++ b/libcxx/include/__bit_reference
@@ -19,7 +19,6 @@
 #include <__iterator/iterator_traits.h>
 #include <__memory/construct_at.h>
 #include <__memory/pointer_traits.h>
-#include <cstring>
 #include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
diff --git a/libcxx/include/__format/format_arg_store.h b/libcxx/include/__format/format_arg_store.h
--- a/libcxx/include/__format/format_arg_store.h
+++ b/libcxx/include/__format/format_arg_store.h
@@ -20,7 +20,6 @@
 #include <__format/concepts.h>
 #include <__format/format_arg.h>
 #include <__utility/forward.h>
-#include <cstring>
 #include <string>
 #include <string_view>
 #include <type_traits>
diff --git a/libcxx/include/__hash_table b/libcxx/include/__hash_table
--- a/libcxx/include/__hash_table
+++ b/libcxx/include/__hash_table
@@ -30,7 +30,6 @@
 #include <__utility/pair.h>
 #include <__utility/swap.h>
 #include <cmath>
-#include <cstring>
 #include <initializer_list>
 #include <type_traits>
 
diff --git a/libcxx/include/__string/char_traits.h b/libcxx/include/__string/char_traits.h
--- a/libcxx/include/__string/char_traits.h
+++ b/libcxx/include/__string/char_traits.h
@@ -18,11 +18,11 @@
 #include <__config>
 #include <__functional/hash.h>
 #include <__iterator/iterator_traits.h>
+#include <__string/constexpr_c_functions.h>
 #include <__type_traits/is_constant_evaluated.h>
 #include <cstddef>
 #include <cstdint>
 #include <cstdio>
-#include <cstring>
 #include <iosfwd>
 
 #ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
diff --git a/libcxx/include/__string/constexpr_c_functions.h b/libcxx/include/__string/constexpr_c_functions.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__string/constexpr_c_functions.h
@@ -0,0 +1,71 @@
+//===----------------------------------------------------------------------===//
+//
+// 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___STRING_CONSTEXPR_C_FUNCTIONS_H
+#define _LIBCPP___STRING_CONSTEXPR_C_FUNCTIONS_H
+
+#include <__config>
+#include <__type_traits/is_constant_evaluated.h>
+#include <cstddef>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 size_t __constexpr_strlen(const char* __str) {
+  // GCC currently doesn't support __builtin_strlen for heap-allocated memory during constant evaluation.
+  // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70816
+#ifdef _LIBCPP_COMPILER_GCC
+  if (__libcpp_is_constant_evaluated()) {
+    size_t __i = 0;
+    for (; __str[__i] != '\0'; ++__i)
+      ;
+    return __i;
+  }
+#endif
+  return __builtin_strlen(__str);
+}
+
+template <class _Tp>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 int
+__constexpr_memcmp(const _Tp* __lhs, const _Tp* __rhs, size_t __count) {
+#ifdef _LIBCPP_COMPILER_GCC
+  if (__libcpp_is_constant_evaluated()) {
+    for (; __count; --__count, ++__lhs, ++__rhs) {
+      if (*__lhs < *__rhs)
+        return -1;
+      if (*__rhs < *__lhs)
+        return 1;
+    }
+    return 0;
+  }
+#endif
+  return __builtin_memcmp(__lhs, __rhs, __count);
+}
+
+inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 const char*
+__constexpr_char_memchr(const char* __str, int __char, size_t __count) {
+#if __has_builtin(__builtin_char_memchr)
+  return __builtin_char_memchr(__str, __char, __count);
+#else
+  if (!__libcpp_is_constant_evaluated())
+    return static_cast<const char*>(std::memchr(__str, __char, __count));
+  for (; __count; --__count) {
+    if (*__str == __char)
+      return __str;
+    ++__str;
+  }
+  return nullptr;
+#endif
+}
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___STRING_CONSTEXPR_C_FUNCTIONS_H
diff --git a/libcxx/include/charconv b/libcxx/include/charconv
--- a/libcxx/include/charconv
+++ b/libcxx/include/charconv
@@ -95,7 +95,6 @@
 #include <cmath> // for log2f
 #include <cstdint>
 #include <cstdlib>
-#include <cstring>
 #include <limits>
 #include <type_traits>
 
@@ -841,6 +840,7 @@
 
 #if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
 #  include <concepts>
+#  include <cstring>
 #  include <iosfwd>
 #endif
 
diff --git a/libcxx/include/cstring b/libcxx/include/cstring
--- a/libcxx/include/cstring
+++ b/libcxx/include/cstring
@@ -100,53 +100,6 @@
 using ::strerror _LIBCPP_USING_IF_EXISTS;
 using ::strlen _LIBCPP_USING_IF_EXISTS;
 
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 size_t __constexpr_strlen(const char* __str) {
-  // GCC currently doesn't support __builtin_strlen for heap-allocated memory during constant evaluation.
-  // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70816
-#ifdef _LIBCPP_COMPILER_GCC
-  if (__libcpp_is_constant_evaluated()) {
-    size_t __i = 0;
-    for (; __str[__i] != '\0'; ++__i)
-      ;
-    return __i;
-  }
-#endif
-  return __builtin_strlen(__str);
-}
-
-template <class _Tp>
-_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 int
-__constexpr_memcmp(const _Tp* __lhs, const _Tp* __rhs, size_t __count) {
-#ifdef _LIBCPP_COMPILER_GCC
-  if (__libcpp_is_constant_evaluated()) {
-    for (; __count; --__count, ++__lhs, ++__rhs) {
-      if (*__lhs < *__rhs)
-        return -1;
-      if (*__rhs < *__lhs)
-        return 1;
-    }
-    return 0;
-  }
-#endif
-  return __builtin_memcmp(__lhs, __rhs, __count);
-}
-
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 const char*
-__constexpr_char_memchr(const char* __str, int __char, size_t __count) {
-#if __has_builtin(__builtin_char_memchr)
-  return __builtin_char_memchr(__str, __char, __count);
-#else
-  if (!__libcpp_is_constant_evaluated())
-    return static_cast<const char*>(std::memchr(__str, __char, __count));
-  for (; __count; --__count) {
-    if (*__str == __char)
-      return __str;
-    ++__str;
-  }
-  return nullptr;
-#endif
-}
-
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_CSTRING
diff --git a/libcxx/include/fstream b/libcxx/include/fstream
--- a/libcxx/include/fstream
+++ b/libcxx/include/fstream
@@ -189,7 +189,6 @@
 #include <__utility/unreachable.h>
 #include <cstdio>
 #include <cstdlib>
-#include <cstring>
 #include <istream>
 #include <ostream>
 #include <typeinfo>
diff --git a/libcxx/include/list b/libcxx/include/list
--- a/libcxx/include/list
+++ b/libcxx/include/list
@@ -207,7 +207,6 @@
 #include <__utility/forward.h>
 #include <__utility/move.h>
 #include <__utility/swap.h>
-#include <cstring>
 #include <limits>
 #include <type_traits>
 #include <version>
diff --git a/libcxx/include/module.modulemap.in b/libcxx/include/module.modulemap.in
--- a/libcxx/include/module.modulemap.in
+++ b/libcxx/include/module.modulemap.in
@@ -1356,6 +1356,7 @@
     export string_view
     module __string {
       module char_traits           { private header "__string/char_traits.h" }
+      module constexpr_c_functions { private header "__string/constexpr_c_functions.h" }
       module extern_template_lists { private header "__string/extern_template_lists.h" }
       module string_fwd            { private header "__fwd/string.h" }
     }
diff --git a/libcxx/include/regex b/libcxx/include/regex
--- a/libcxx/include/regex
+++ b/libcxx/include/regex
@@ -773,7 +773,6 @@
 #include <__utility/move.h>
 #include <__utility/pair.h>
 #include <__utility/swap.h>
-#include <cstring>
 #include <deque>
 #include <stdexcept>
 #include <string>
diff --git a/libcxx/include/string b/libcxx/include/string
--- a/libcxx/include/string
+++ b/libcxx/include/string
@@ -570,7 +570,6 @@
 #include <cstdint>
 #include <cstdio>  // EOF
 #include <cstdlib>
-#include <cstring>
 #include <limits>
 #include <stdexcept>
 #include <string_view>
diff --git a/libcxx/include/vector b/libcxx/include/vector
--- a/libcxx/include/vector
+++ b/libcxx/include/vector
@@ -314,7 +314,6 @@
 #include <__utility/swap.h>
 #include <climits>
 #include <cstdlib>
-#include <cstring>
 #include <iosfwd> // for forward declaration of vector
 #include <limits>
 #include <stdexcept>
diff --git a/libcxx/src/include/ryu/common.h b/libcxx/src/include/ryu/common.h
--- a/libcxx/src/include/ryu/common.h
+++ b/libcxx/src/include/ryu/common.h
@@ -43,7 +43,8 @@
 // clang-format off
 
 #include <__assert>
-#include "__config"
+#include <__config>
+#include <cstring>
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
diff --git a/libcxx/test/libcxx/private_headers.verify.cpp b/libcxx/test/libcxx/private_headers.verify.cpp
--- a/libcxx/test/libcxx/private_headers.verify.cpp
+++ b/libcxx/test/libcxx/private_headers.verify.cpp
@@ -571,6 +571,7 @@
 #include <__split_buffer> // expected-error@*:* {{use of private header from outside its module: '__split_buffer'}}
 #include <__std_stream> // expected-error@*:* {{use of private header from outside its module: '__std_stream'}}
 #include <__string/char_traits.h> // expected-error@*:* {{use of private header from outside its module: '__string/char_traits.h'}}
+#include <__string/constexpr_c_functions.h> // expected-error@*:* {{use of private header from outside its module: '__string/constexpr_c_functions.h'}}
 #include <__string/extern_template_lists.h> // expected-error@*:* {{use of private header from outside its module: '__string/extern_template_lists.h'}}
 #include <__thread/poll_with_backoff.h> // expected-error@*:* {{use of private header from outside its module: '__thread/poll_with_backoff.h'}}
 #include <__thread/timed_backoff_policy.h> // expected-error@*:* {{use of private header from outside its module: '__thread/timed_backoff_policy.h'}}
diff --git a/libcxx/test/libcxx/strings/c.strings/constexpr.cstring.compile.pass.cpp b/libcxx/test/libcxx/strings/c.strings/constexpr.cstring.compile.pass.cpp
--- a/libcxx/test/libcxx/strings/c.strings/constexpr.cstring.compile.pass.cpp
+++ b/libcxx/test/libcxx/strings/c.strings/constexpr.cstring.compile.pass.cpp
@@ -8,9 +8,11 @@
 
 // UNSUPPORTED: c++03, c++11
 
+// ADDITIONAL_COMPILE_FLAGS: -Wno-private-header
+
 // Check that __constexpr_* cstring functions are actually constexpr
 
-#include <cstring>
+#include <__string/constexpr_c_functions.h>
 
 static_assert(std::__constexpr_strlen("Banane") == 6, "");
 static_assert(std::__constexpr_memcmp("Banane", "Banand", 6) == 1, "");
diff --git a/libcxx/test/libcxx/transitive_includes/cxx03.csv b/libcxx/test/libcxx/transitive_includes/cxx03.csv
--- a/libcxx/test/libcxx/transitive_includes/cxx03.csv
+++ b/libcxx/test/libcxx/transitive_includes/cxx03.csv
@@ -327,7 +327,6 @@
 format cstddef
 format cstdint
 format cstdlib
-format cstring
 format initializer_list
 format limits
 format locale
diff --git a/libcxx/test/libcxx/transitive_includes/cxx11.csv b/libcxx/test/libcxx/transitive_includes/cxx11.csv
--- a/libcxx/test/libcxx/transitive_includes/cxx11.csv
+++ b/libcxx/test/libcxx/transitive_includes/cxx11.csv
@@ -327,7 +327,6 @@
 format cstddef
 format cstdint
 format cstdlib
-format cstring
 format initializer_list
 format limits
 format locale
diff --git a/libcxx/test/libcxx/transitive_includes/cxx14.csv b/libcxx/test/libcxx/transitive_includes/cxx14.csv
--- a/libcxx/test/libcxx/transitive_includes/cxx14.csv
+++ b/libcxx/test/libcxx/transitive_includes/cxx14.csv
@@ -329,7 +329,6 @@
 format cstddef
 format cstdint
 format cstdlib
-format cstring
 format initializer_list
 format limits
 format locale
diff --git a/libcxx/test/libcxx/transitive_includes/cxx17.csv b/libcxx/test/libcxx/transitive_includes/cxx17.csv
--- a/libcxx/test/libcxx/transitive_includes/cxx17.csv
+++ b/libcxx/test/libcxx/transitive_includes/cxx17.csv
@@ -329,7 +329,6 @@
 format cstddef
 format cstdint
 format cstdlib
-format cstring
 format initializer_list
 format limits
 format locale
diff --git a/libcxx/test/libcxx/transitive_includes/cxx20.csv b/libcxx/test/libcxx/transitive_includes/cxx20.csv
--- a/libcxx/test/libcxx/transitive_includes/cxx20.csv
+++ b/libcxx/test/libcxx/transitive_includes/cxx20.csv
@@ -338,7 +338,6 @@
 format cstddef
 format cstdint
 format cstdlib
-format cstring
 format initializer_list
 format limits
 format locale
diff --git a/libcxx/test/libcxx/transitive_includes/cxx2b.csv b/libcxx/test/libcxx/transitive_includes/cxx2b.csv
--- a/libcxx/test/libcxx/transitive_includes/cxx2b.csv
+++ b/libcxx/test/libcxx/transitive_includes/cxx2b.csv
@@ -69,7 +69,6 @@
 charconv cstddef
 charconv cstdint
 charconv cstdlib
-charconv cstring
 charconv initializer_list
 charconv limits
 charconv type_traits
@@ -81,7 +80,6 @@
 chrono cstddef
 chrono cstdint
 chrono cstdlib
-chrono cstring
 chrono ctime
 chrono initializer_list
 chrono limits
@@ -261,7 +259,6 @@
 format cstddef
 format cstdint
 format cstdlib
-format cstring
 format initializer_list
 format limits
 format locale