diff --git a/libcxx/CMakeLists.txt b/libcxx/CMakeLists.txt
--- a/libcxx/CMakeLists.txt
+++ b/libcxx/CMakeLists.txt
@@ -287,6 +287,12 @@
     "Build libc++ with an externalized threading library.
      This option may only be set to ON when LIBCXX_ENABLE_THREADS=ON" OFF)
 
+if (LIBCXX_ENABLE_THREADS)
+  set(LIBCXX_PSTL_CPU_BACKEND "std_thread" CACHE STRING "Which PSTL CPU backend to use")
+else()
+  set(LIBCXX_PSTL_CPU_BACKEND "serial" CACHE STRING "Which PSTL CPU backend to use")
+endif()
+
 # Misc options ----------------------------------------------------------------
 # FIXME: Turn -pedantic back ON. It is currently off because it warns
 # about #include_next which is used everywhere.
@@ -796,6 +802,15 @@
   config_define(0 _LIBCPP_ENABLE_ASSERTIONS_DEFAULT)
 endif()
 
+if (LIBCXX_PSTL_CPU_BACKEND STREQUAL "serial")
+  config_define(1 _LIBCPP_PSTL_CPU_BACKEND_SERIAL)
+elseif(LIBCXX_PSTL_CPU_BACKEND STREQUAL "std_thread")
+  config_define(1 _LIBCPP_PSTL_CPU_BACKEND_THREAD)
+else()
+  message(FATAL_ERROR "LIBCXX_PSTL_CPU_BACKEND is set to ${LIBCXX_PSTL_CPU_BACKEND}, which is not a valid backend.
+                       Valid backends are: serial, std_thread")
+endif()
+
 if (LIBCXX_ABI_DEFINES)
   set(abi_defines)
   foreach (abi_define ${LIBCXX_ABI_DEFINES})
diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -78,6 +78,7 @@
   __algorithm/pstl_backends/cpu_backends/find_if.h
   __algorithm/pstl_backends/cpu_backends/for_each.h
   __algorithm/pstl_backends/cpu_backends/serial.h
+  __algorithm/pstl_backends/cpu_backends/thread.h
   __algorithm/pstl_backends/cpu_backends/transform.h
   __algorithm/pstl_copy.h
   __algorithm/pstl_fill.h
diff --git a/libcxx/include/__algorithm/pstl_backend.h b/libcxx/include/__algorithm/pstl_backend.h
--- a/libcxx/include/__algorithm/pstl_backend.h
+++ b/libcxx/include/__algorithm/pstl_backend.h
@@ -85,7 +85,8 @@
 };
 #  endif
 
-#  if defined(_PSTL_CPU_BACKEND_SERIAL)
+#  if defined(_LIBCPP_PSTL_CPU_BACKEND_SERIAL) || defined(_LIBCPP_PSTL_CPU_BACKEND_THREAD)
+#    include <__algorithm/pstl_backends/cpu_backend.h>
 template <>
 struct __select_backend<std::execution::parallel_policy> {
   using type = __cpu_backend_tag;
diff --git a/libcxx/include/__algorithm/pstl_backends/cpu_backends/backend.h b/libcxx/include/__algorithm/pstl_backends/cpu_backends/backend.h
--- a/libcxx/include/__algorithm/pstl_backends/cpu_backends/backend.h
+++ b/libcxx/include/__algorithm/pstl_backends/cpu_backends/backend.h
@@ -11,8 +11,10 @@
 
 #include <__config>
 
-#if defined(_LIBCPP_HAS_NO_THREADS) || defined(_PSTL_CPU_BACKEND_SERIAL)
+#if defined(_LIBCPP_PSTL_CPU_BACKEND_SERIAL)
 #  include <__algorithm/pstl_backends/cpu_backends/serial.h>
+#elif defined(_LIBCPP_PSTL_CPU_BACKEND_THREAD)
+#  include <__algorithm/pstl_backends/cpu_backends/thread.h>
 #else
 #  error "Invalid CPU backend choice"
 #endif
diff --git a/libcxx/include/__algorithm/pstl_backends/cpu_backends/thread.h b/libcxx/include/__algorithm/pstl_backends/cpu_backends/thread.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__algorithm/pstl_backends/cpu_backends/thread.h
@@ -0,0 +1,65 @@
+//===----------------------------------------------------------------------===//
+//
+// 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___ALGORITHM_PSTL_BACKENDS_CPU_BACKENDS_THREAD_H
+#define _LIBCPP___ALGORITHM_PSTL_BACKENDS_CPU_BACKENDS_THREAD_H
+
+#include <__assert>
+#include <__config>
+#include <thread>
+#include <vector>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+#if !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+namespace __par_backend::inline __thread_cpu_backend {
+
+template <class _RandomAccessIterator, class _Fp>
+_LIBCPP_HIDE_FROM_ABI void __parallel_for(_RandomAccessIterator __first, _RandomAccessIterator __last, _Fp __f) {
+  vector<thread> __threads;
+  __threads.reserve([]() {
+    auto __max_thread_count = thread::hardware_concurrency();
+    return __max_thread_count == 0 ? 1 : __max_thread_count;
+  }());
+
+  const auto __brick_size = ((__last - __first) / __threads.capacity()) + 1;
+
+  for (size_t __i = 0; __i != __threads.capacity(); ++__i) {
+    if (__last - __first >= __brick_size) {
+      __threads.emplace_back([&__f, __brick_first = __first, __brick_last = __first + __brick_size]() {
+        __f(__brick_first, __brick_last);
+      });
+      __first += __brick_size;
+    } else {
+      __threads.emplace_back([&__f, __brick_first = __first, __brick_last = __last]() {
+        __f(__brick_first, __brick_last);
+      });
+      __first = __last;
+    }
+  }
+  _LIBCPP_ASSERT(__first == __last, "__parallel_for didn't iterator over all elements!");
+
+  for (auto& __el : __threads) {
+    __el.join();
+  }
+}
+
+_LIBCPP_HIDE_FROM_ABI inline void __cancel_execution() {}
+
+} // namespace __par_backend::inline __thread_cpu_backend
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && && _LIBCPP_STD_VER >= 17
+
+#endif // _LIBCPP___ALGORITHM_PSTL_BACKENDS_CPU_BACKENDS_THREAD_H
diff --git a/libcxx/include/__config b/libcxx/include/__config
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -1273,7 +1273,6 @@
 
 // TODO: Make this a proper configuration option
 #define _PSTL_PAR_BACKEND_SERIAL
-#define _PSTL_CPU_BACKEND_SERIAL
 
 #define _PSTL_PRAGMA(x) _Pragma(#    x)
 
diff --git a/libcxx/include/__config_site.in b/libcxx/include/__config_site.in
--- a/libcxx/include/__config_site.in
+++ b/libcxx/include/__config_site.in
@@ -32,6 +32,10 @@
 #cmakedefine01 _LIBCPP_ENABLE_ASSERTIONS_DEFAULT
 #cmakedefine _LIBCPP_ENABLE_DEBUG_MODE
 
+// PSTL backends
+#cmakedefine _LIBCPP_PSTL_CPU_BACKEND_SERIAL
+#cmakedefine _LIBCPP_PSTL_CPU_BACKEND_THREAD
+
 // __USE_MINGW_ANSI_STDIO gets redefined on MinGW
 #ifdef __clang__
 #  pragma clang diagnostic push
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
@@ -341,6 +341,9 @@
       module pstl_backends_cpu_backends_serial {
         private header "__algorithm/pstl_backends/cpu_backends/serial.h"
       }
+      module pstl_backends_cpu_backends_thread {
+        private header "__algorithm/pstl_backends/cpu_backends/thread.h"
+      }
       module pstl_backends_cpu_backends_transform {
         private header "__algorithm/pstl_backends/cpu_backends/transform.h"
       }
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
@@ -121,6 +121,7 @@
 #include <__algorithm/pstl_backends/cpu_backends/find_if.h> // expected-error@*:* {{use of private header from outside its module: '__algorithm/pstl_backends/cpu_backends/find_if.h'}}
 #include <__algorithm/pstl_backends/cpu_backends/for_each.h> // expected-error@*:* {{use of private header from outside its module: '__algorithm/pstl_backends/cpu_backends/for_each.h'}}
 #include <__algorithm/pstl_backends/cpu_backends/serial.h> // expected-error@*:* {{use of private header from outside its module: '__algorithm/pstl_backends/cpu_backends/serial.h'}}
+#include <__algorithm/pstl_backends/cpu_backends/thread.h> // expected-error@*:* {{use of private header from outside its module: '__algorithm/pstl_backends/cpu_backends/thread.h'}}
 #include <__algorithm/pstl_backends/cpu_backends/transform.h> // expected-error@*:* {{use of private header from outside its module: '__algorithm/pstl_backends/cpu_backends/transform.h'}}
 #include <__algorithm/push_heap.h> // expected-error@*:* {{use of private header from outside its module: '__algorithm/push_heap.h'}}
 #include <__algorithm/ranges_adjacent_find.h> // expected-error@*:* {{use of private header from outside its module: '__algorithm/ranges_adjacent_find.h'}}
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
@@ -16,6 +16,8 @@
 algorithm new
 algorithm ratio
 algorithm stdexcept
+algorithm tuple
+algorithm typeinfo
 algorithm type_traits
 algorithm utility
 algorithm version
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
@@ -16,6 +16,8 @@
 algorithm new
 algorithm ratio
 algorithm stdexcept
+algorithm tuple
+algorithm typeinfo
 algorithm type_traits
 algorithm utility
 algorithm version
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
@@ -16,6 +16,8 @@
 algorithm new
 algorithm ratio
 algorithm stdexcept
+algorithm tuple
+algorithm typeinfo
 algorithm type_traits
 algorithm utility
 algorithm version
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
@@ -16,6 +16,8 @@
 algorithm new
 algorithm ratio
 algorithm stdexcept
+algorithm tuple
+algorithm typeinfo
 algorithm type_traits
 algorithm utility
 algorithm version
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
@@ -16,6 +16,8 @@
 algorithm new
 algorithm ratio
 algorithm stdexcept
+algorithm tuple
+algorithm typeinfo
 algorithm type_traits
 algorithm utility
 algorithm version
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
@@ -9,6 +9,8 @@
 algorithm limits
 algorithm new
 algorithm ratio
+algorithm tuple
+algorithm typeinfo
 algorithm version
 any cstddef
 any cstdint