diff --git a/libcxx/CMakeLists.txt b/libcxx/CMakeLists.txt
--- a/libcxx/CMakeLists.txt
+++ b/libcxx/CMakeLists.txt
@@ -114,7 +114,11 @@
   endif()
 else()
   if (LIBCXX_ENABLE_SHARED)
-    set(LIBCXX_DEFAULT_TEST_CONFIG "llvm-libc++-shared.cfg.in")
+    if (LIBCXX_ENABLE_PARALLEL_ALGORITHMS)
+      set(LIBCXX_DEFAULT_TEST_CONFIG "llvm-libc++-with-pstl.cfg.in")
+    else()
+      set(LIBCXX_DEFAULT_TEST_CONFIG "llvm-libc++-shared.cfg.in")
+    endif()
   else()
     set(LIBCXX_DEFAULT_TEST_CONFIG "llvm-libc++-static.cfg.in")
   endif()
@@ -490,6 +494,12 @@
   set(LIBCXX_DEBUG_BUILD OFF)
 endif()
 
+# PSTL Configuration ===========================================================
+if (LIBCXX_ENABLE_PARALLEL_ALGORITHMS)
+    get_target_property(LIBCXX_PSTL_SOURCE_DIR pstl::ParallelSTL SOURCE_DIRECTORY)
+    get_target_property(LIBCXX_PSTL_GENERATED_SOURCE_DIR pstl::ParallelSTL GENERATED_DIRECTORY)
+endif()
+
 #===============================================================================
 # Setup Compiler Flags
 #===============================================================================
diff --git a/libcxx/include/algorithm b/libcxx/include/algorithm
--- a/libcxx/include/algorithm
+++ b/libcxx/include/algorithm
@@ -774,7 +774,7 @@
       set_symmetric_difference(I1 first1, S1 last1, I2 first2, S2 last2, O result,
                                Comp comp = {}, Proj1 proj1 = {},
                                Proj2 proj2 = {});                                                   // since C++20
-  
+
   template<input_range R1, input_range R2, weakly_incrementable O,
            class Comp = ranges::less, class Proj1 = identity, class Proj2 = identity>
     requires mergeable<iterator_t<R1>, iterator_t<R2>, O, Comp, Proj1, Proj2>
@@ -787,13 +787,13 @@
            indirect_strict_weak_order<const T*, projected<I, Proj>> Comp = ranges::less>
     constexpr subrange<I>
       equal_range(I first, S last, const T& value, Comp comp = {}, Proj proj = {});                 // since C++20
-  
+
   template<forward_range R, class T, class Proj = identity,
            indirect_strict_weak_order<const T*, projected<iterator_t<R>, Proj>> Comp =
              ranges::less>
     constexpr borrowed_subrange_t<R>
       equal_range(R&& r, const T& value, Comp comp = {}, Proj proj = {});                           // since C++20
-  
+
   template<class I1, class I2, class O>
     using set_union_result = in_in_out_result<I1, I2, O>;                                           // since C++20
 
@@ -818,7 +818,7 @@
              ranges::less>
     constexpr bool includes(I1 first1, S1 last1, I2 first2, S2 last2, Comp comp = {},
                             Proj1 proj1 = {}, Proj2 proj2 = {});                                   // Since C++20
-  
+
   template<input_range R1, input_range R2, class Proj1 = identity,
            class Proj2 = identity,
            indirect_strict_weak_order<projected<iterator_t<R1>, Proj1>,
@@ -1669,7 +1669,9 @@
 #endif
 
 #if defined(_LIBCPP_HAS_PARALLEL_ALGORITHMS) && _LIBCPP_STD_VER >= 17
-#   include <__pstl_algorithm>
+// TODO: Remove this include once we fix transitive includes of <algorithm>
+#  include <__functional/not_fn.h>
+#  include <__pstl_algorithm>
 #endif
 
 #endif // _LIBCPP_ALGORITHM
diff --git a/libcxx/include/unordered_map b/libcxx/include/unordered_map
--- a/libcxx/include/unordered_map
+++ b/libcxx/include/unordered_map
@@ -532,7 +532,6 @@
 #include <version>
 
 #ifndef _LIBCPP_REMOVE_TRANSITIVE_INCLUDES
-#  include <algorithm>
 #  include <bit>
 #  include <iterator>
 #endif
diff --git a/libcxx/src/CMakeLists.txt b/libcxx/src/CMakeLists.txt
--- a/libcxx/src/CMakeLists.txt
+++ b/libcxx/src/CMakeLists.txt
@@ -186,6 +186,7 @@
 endif()
 
 function(cxx_set_common_defines name)
+# PSTL configuration ===========================================================
   if (LIBCXX_ENABLE_PARALLEL_ALGORITHMS)
     target_link_libraries(${name} PUBLIC pstl::ParallelSTL)
   endif()
diff --git a/libcxx/test/configs/cmake-bridge.cfg.in b/libcxx/test/configs/cmake-bridge.cfg.in
--- a/libcxx/test/configs/cmake-bridge.cfg.in
+++ b/libcxx/test/configs/cmake-bridge.cfg.in
@@ -27,6 +27,8 @@
 config.substitutions.append(('%{cxx}', shlex.quote('@CMAKE_CXX_COMPILER@')))
 config.substitutions.append(('%{libcxx}', '@LIBCXX_SOURCE_DIR@'))
 config.substitutions.append(('%{include}', '@LIBCXX_GENERATED_INCLUDE_DIR@'))
+config.substitutions.append(('%{pstl-include}', '@LIBCXX_PSTL_SOURCE_DIR@'))
+config.substitutions.append(('%{pstl-generated-include}', '@LIBCXX_PSTL_GENERATED_SOURCE_DIR@'))
 config.substitutions.append(('%{target-include}', '@LIBCXX_GENERATED_INCLUDE_TARGET_DIR@'))
 config.substitutions.append(('%{lib}', '@LIBCXX_LIBRARY_DIR@'))
 config.substitutions.append(('%{executor}', '@LIBCXX_EXECUTOR@'))
diff --git a/libcxx/test/configs/llvm-libc++-with-pstl.cfg.in b/libcxx/test/configs/llvm-libc++-with-pstl.cfg.in
new file mode 100644
--- /dev/null
+++ b/libcxx/test/configs/llvm-libc++-with-pstl.cfg.in
@@ -0,0 +1,27 @@
+# This testing configuration handles running the test suite against LLVM's libc++
+# using a shared library.
+
+lit_config.load_config(config, '@CMAKE_CURRENT_BINARY_DIR@/cmake-bridge.cfg')
+
+config.substitutions.append(('%{flags}',
+    '-isysroot {}'.format('@CMAKE_OSX_SYSROOT@') if '@CMAKE_OSX_SYSROOT@' else ''
+))
+config.substitutions.append(('%{compile_flags}',
+    '-nostdinc++ -I %{include} -I %{target-include} -I %{pstl-include} -I %{pstl-generated-include} -I %{libcxx}/test/support'
+))
+config.substitutions.append(('%{link_flags}',
+    '-nostdlib++ -L %{lib} -Wl,-rpath,%{lib} -lc++ -pthread'
+))
+config.substitutions.append(('%{exec}',
+    '%{executor} --execdir %T -- '
+))
+
+import os, site
+site.addsitedir(os.path.join('@LIBCXX_SOURCE_DIR@', 'utils'))
+import libcxx.test.params, libcxx.test.newconfig
+libcxx.test.newconfig.configure(
+    libcxx.test.params.DEFAULT_PARAMETERS,
+    libcxx.test.features.DEFAULT_FEATURES,
+    config,
+    lit_config
+)
diff --git a/libcxx/test/libcxx/clang_tidy.sh.cpp b/libcxx/test/libcxx/clang_tidy.sh.cpp
--- a/libcxx/test/libcxx/clang_tidy.sh.cpp
+++ b/libcxx/test/libcxx/clang_tidy.sh.cpp
@@ -8,6 +8,8 @@
 
 // REQUIRES: has-clang-tidy
 
+// XFAIL: with-pstl
+
 // TODO: run clang-tidy with modules enabled once they are supported
 // RUN: clang-tidy %s --warnings-as-errors=* -header-filter=.* --config-file=%S/../../.clang-tidy -- -Wweak-vtables -Wno-unknown-warning-option %{compile_flags} -fno-modules
 // -Wno-unknown-warning-option tells clang-tidy to ignore '-W' command-line arguments that it doesn't know.
diff --git a/libcxx/test/libcxx/min_max_macros.compile.pass.cpp b/libcxx/test/libcxx/min_max_macros.compile.pass.cpp
--- a/libcxx/test/libcxx/min_max_macros.compile.pass.cpp
+++ b/libcxx/test/libcxx/min_max_macros.compile.pass.cpp
@@ -12,6 +12,8 @@
 // The system-provided <uchar.h> seems to be broken on AIX
 // XFAIL: LIBCXX-AIX-FIXME
 
+// XFAIL: with-pstl
+
 // Prevent <ext/hash_map> from generating deprecated warnings for this test.
 #if defined(__DEPRECATED)
 #    undef __DEPRECATED
diff --git a/libcxx/test/libcxx/nasty_macros.compile.pass.cpp b/libcxx/test/libcxx/nasty_macros.compile.pass.cpp
--- a/libcxx/test/libcxx/nasty_macros.compile.pass.cpp
+++ b/libcxx/test/libcxx/nasty_macros.compile.pass.cpp
@@ -12,6 +12,8 @@
 // The system-provided <uchar.h> seems to be broken on AIX
 // XFAIL: LIBCXX-AIX-FIXME
 
+// XFAIL: with-pstl
+
 // Prevent <ext/hash_map> from generating deprecated warnings for this test.
 #if defined(__DEPRECATED)
 #    undef __DEPRECATED
diff --git a/libcxx/test/libcxx/transitive_includes/expected.unordered_map b/libcxx/test/libcxx/transitive_includes/expected.unordered_map
--- a/libcxx/test/libcxx/transitive_includes/expected.unordered_map
+++ b/libcxx/test/libcxx/transitive_includes/expected.unordered_map
@@ -1,4 +1,3 @@
-algorithm
 atomic
 bit
 chrono
diff --git a/libcxx/utils/ci/buildkite-pipeline.yml b/libcxx/utils/ci/buildkite-pipeline.yml
--- a/libcxx/utils/ci/buildkite-pipeline.yml
+++ b/libcxx/utils/ci/buildkite-pipeline.yml
@@ -392,6 +392,19 @@
           limit: 2
     timeout_in_minutes: 120
 
+  - label: "With PSTL support"
+    command: "libcxx/utils/ci/run-buildbot with-pstl"
+    artifact_paths:
+      - "**/test-results.xml"
+    agents:
+      queue: "libcxx-builders"
+      os: "linux"
+    retry:
+      automatic:
+        - exit_status: -1  # Agent was lost
+          limit: 2
+    timeout_in_minutes: 120
+
   - label: "No transitive includes"
     command: "libcxx/utils/ci/run-buildbot generic-no-transitive-includes"
     artifact_paths:
diff --git a/libcxx/utils/ci/run-buildbot b/libcxx/utils/ci/run-buildbot
--- a/libcxx/utils/ci/run-buildbot
+++ b/libcxx/utils/ci/run-buildbot
@@ -92,7 +92,7 @@
 
 function generate-cmake() {
     generate-cmake-base \
-          -DLLVM_ENABLE_RUNTIMES="libcxx;libcxxabi;libunwind" \
+          -DLLVM_ENABLE_RUNTIMES="pstl;libcxx;libcxxabi;libunwind" \
           -DLIBCXX_CXX_ABI=libcxxabi \
           "${@}"
 }
@@ -369,6 +369,15 @@
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-abi-unstable.cmake"
     check-runtimes
 ;;
+with-pstl)
+    clean
+    generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-cxx20.cmake" \
+                   -DLIBCXX_TEST_CONFIG="llvm-libc++-with-pstl.cfg.in" \
+                   -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in" \
+                   -DCMAKE_BUILD_WITH_INSTALL_RPATH=TRUE \
+                   -DLIBCXX_ENABLE_PARALLEL_ALGORITHMS=ON
+    check-runtimes
+;;
 apple-system)
     clean
 
diff --git a/libcxx/utils/libcxx/test/features.py b/libcxx/utils/libcxx/test/features.py
--- a/libcxx/utils/libcxx/test/features.py
+++ b/libcxx/utils/libcxx/test/features.py
@@ -190,6 +190,7 @@
   '_LIBCPP_HAS_NO_WIDE_CHARACTERS': 'no-wide-characters',
   '_LIBCPP_HAS_NO_UNICODE': 'libcpp-has-no-unicode',
   '_LIBCPP_ENABLE_DEBUG_MODE': 'libcpp-has-debug-mode',
+  '_LIBCPP_HAS_PARALLEL_ALGORITHMS': 'with-pstl',
 }
 for macro, feature in macros.items():
   DEFAULT_FEATURES.append(
diff --git a/libcxxabi/CMakeLists.txt b/libcxxabi/CMakeLists.txt
--- a/libcxxabi/CMakeLists.txt
+++ b/libcxxabi/CMakeLists.txt
@@ -155,7 +155,11 @@
   endif()
 else()
   if (LIBCXXABI_ENABLE_SHARED)
-    set(LIBCXXABI_DEFAULT_TEST_CONFIG "llvm-libc++abi-shared.cfg.in")
+    if (LIBCXX_ENABLE_PARALLEL_ALGORITHMS)
+      set(LIBCXXABI_DEFAULT_TEST_CONFIG "llvm-libc++abi-with-pstl.cfg.in")
+    else()
+      set(LIBCXXABI_DEFAULT_TEST_CONFIG "llvm-libc++abi-shared.cfg.in")
+    endif()
   else()
     set(LIBCXXABI_DEFAULT_TEST_CONFIG "llvm-libc++abi-static.cfg.in")
   endif()
@@ -232,6 +236,12 @@
 # Include macros for adding and removing libc++abi flags.
 include(HandleLibcxxabiFlags)
 
+# PSTL Configuration ===========================================================
+if (LIBCXX_ENABLE_PARALLEL_ALGORITHMS)
+    get_target_property(LIBCXXABI_PSTL_SOURCE_DIR pstl::ParallelSTL SOURCE_DIRECTORY)
+    get_target_property(LIBCXXABI_PSTL_GENERATED_SOURCE_DIR pstl::ParallelSTL GENERATED_DIRECTORY)
+endif()
+
 #===============================================================================
 # Setup Compiler Flags
 #===============================================================================
diff --git a/libcxxabi/src/CMakeLists.txt b/libcxxabi/src/CMakeLists.txt
--- a/libcxxabi/src/CMakeLists.txt
+++ b/libcxxabi/src/CMakeLists.txt
@@ -160,6 +160,9 @@
 
 # Build the shared library.
 add_library(cxxabi_shared_objects OBJECT EXCLUDE_FROM_ALL ${LIBCXXABI_SOURCES} ${LIBCXXABI_HEADERS})
+if (TARGET pstl::ParallelSTL)
+  target_link_libraries(cxxabi_shared_objects PUBLIC pstl::ParallelSTL)
+endif()
 if (LIBCXXABI_USE_LLVM_UNWINDER)
   if (LIBCXXABI_STATICALLY_LINK_UNWINDER_IN_SHARED_LIBRARY)
     target_link_libraries(cxxabi_shared_objects PUBLIC unwind_shared_objects) # propagate usage requirements
@@ -235,6 +238,9 @@
 
 # Build the static library.
 add_library(cxxabi_static_objects OBJECT EXCLUDE_FROM_ALL ${LIBCXXABI_SOURCES} ${LIBCXXABI_HEADERS})
+if (TARGET pstl::ParallelSTL)
+  target_link_libraries(cxxabi_static_objects PUBLIC pstl::ParallelSTL)
+endif()
 if (LIBCXXABI_USE_LLVM_UNWINDER AND LIBCXXABI_STATICALLY_LINK_UNWINDER_IN_STATIC_LIBRARY)
   target_link_libraries(cxxabi_static_objects PUBLIC unwind_static_objects) # propagate usage requirements
   target_sources(cxxabi_static_objects PUBLIC $<TARGET_OBJECTS:unwind_static_objects>)
diff --git a/libcxxabi/test/configs/cmake-bridge.cfg.in b/libcxxabi/test/configs/cmake-bridge.cfg.in
--- a/libcxxabi/test/configs/cmake-bridge.cfg.in
+++ b/libcxxabi/test/configs/cmake-bridge.cfg.in
@@ -31,6 +31,8 @@
 config.substitutions.append(('%{include}', '@LIBCXXABI_SOURCE_DIR@/include'))
 config.substitutions.append(('%{cxx-include}', '@LIBCXXABI_HEADER_DIR@/include/c++/v1'))
 config.substitutions.append(('%{cxx-target-include}', '@LIBCXXABI_HEADER_DIR@/include/%{triple}/c++/v1'))
+config.substitutions.append(('%{pstl-include}', '@LIBCXXABI_PSTL_SOURCE_DIR@'))
+config.substitutions.append(('%{pstl-generated-include}', '@LIBCXXABI_PSTL_GENERATED_SOURCE_DIR@'))
 config.substitutions.append(('%{lib}', '@LIBCXXABI_LIBRARY_DIR@'))
 config.substitutions.append(('%{executor}', '@LIBCXXABI_EXECUTOR@'))
 
diff --git a/libcxxabi/test/configs/llvm-libc++abi-with-pstl.cfg.in b/libcxxabi/test/configs/llvm-libc++abi-with-pstl.cfg.in
new file mode 100644
--- /dev/null
+++ b/libcxxabi/test/configs/llvm-libc++abi-with-pstl.cfg.in
@@ -0,0 +1,27 @@
+# This testing configuration handles running the test suite against LLVM's libc++abi
+# using a shared library.
+
+lit_config.load_config(config, '@CMAKE_CURRENT_BINARY_DIR@/cmake-bridge.cfg')
+
+config.substitutions.append(('%{flags}',
+    '-isysroot {}'.format('@CMAKE_OSX_SYSROOT@') if '@CMAKE_OSX_SYSROOT@' else ''
+))
+config.substitutions.append(('%{compile_flags}',
+    '-nostdinc++ -I %{include} -I %{pstl-include} -I %{pstl-generated-include} -I %{cxx-include} -I %{cxx-target-include} %{maybe-include-libunwind} -I %{libcxx}/test/support -I %{libcxx}/src -D_LIBCPP_ENABLE_CXX17_REMOVED_UNEXPECTED_FUNCTIONS'
+))
+config.substitutions.append(('%{link_flags}',
+    '-nostdlib++ -L %{lib} -Wl,-rpath,%{lib} -lc++ -lc++abi -pthread'
+))
+config.substitutions.append(('%{exec}',
+    '%{executor} --execdir %T -- '
+))
+
+import os, site
+site.addsitedir(os.path.join('@LIBCXXABI_LIBCXX_PATH@', 'utils'))
+import libcxx.test.params, libcxx.test.newconfig
+libcxx.test.newconfig.configure(
+    libcxx.test.params.DEFAULT_PARAMETERS,
+    libcxx.test.features.DEFAULT_FEATURES,
+    config,
+    lit_config
+)
diff --git a/pstl/CMakeLists.txt b/pstl/CMakeLists.txt
--- a/pstl/CMakeLists.txt
+++ b/pstl/CMakeLists.txt
@@ -66,6 +66,11 @@
     $<BUILD_INTERFACE:${PSTL_GENERATED_HEADERS_DIR}>
     $<INSTALL_INTERFACE:include>)
 
+set_target_properties(ParallelSTL PROPERTIES
+                      SOURCE_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/include
+                      GENERATED_DIRECTORY ${PSTL_GENERATED_HEADERS_DIR}
+                     )
+
 ###############################################################################
 # Setup tests
 ###############################################################################
diff --git a/pstl/include/pstl/internal/algorithm_impl.h b/pstl/include/pstl/internal/algorithm_impl.h
--- a/pstl/include/pstl/internal/algorithm_impl.h
+++ b/pstl/include/pstl/internal/algorithm_impl.h
@@ -536,7 +536,7 @@
 
 template <class _Tag, class _ExecutionPolicy, class _ForwardIterator, class _Predicate>
 _ForwardIterator
-__pattern_find_if(_Tag __tag, _ExecutionPolicy&&, _ForwardIterator __first, _ForwardIterator __last,
+__pattern_find_if(_Tag, _ExecutionPolicy&&, _ForwardIterator __first, _ForwardIterator __last,
                   _Predicate __pred) noexcept
 {
     return __internal::__brick_find_if(__first, __last, __pred, typename _Tag::__is_vector{});
diff --git a/pstl/include/pstl/internal/undef_macros.h b/pstl/include/pstl/internal/undef_macros.h
new file mode 100644
--- /dev/null
+++ b/pstl/include/pstl/internal/undef_macros.h
@@ -0,0 +1,15 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifdef min
+#  undef min
+#endif
+
+#ifdef max
+#  undef max
+#endif
diff --git a/pstl/include/pstl/internal/utils.h b/pstl/include/pstl/internal/utils.h
--- a/pstl/include/pstl/internal/utils.h
+++ b/pstl/include/pstl/internal/utils.h
@@ -24,6 +24,7 @@
 auto
 __except_handler(_Fp __f) -> decltype(__f())
 {
+#if defined(__cpp_exceptions) && __cpp_exceptions >= 199711L
     try
     {
         return __f();
@@ -36,6 +37,9 @@
     {
         std::terminate(); // Good bye according to the standard [algorithms.parallel.exceptions]
     }
+#else
+    return __f();
+#endif // defined(__cpp_exceptions) && __cpp_exceptions >= 199711L
 }
 
 template <typename _Fp>
diff --git a/runtimes/CMakeLists.txt b/runtimes/CMakeLists.txt
--- a/runtimes/CMakeLists.txt
+++ b/runtimes/CMakeLists.txt
@@ -15,7 +15,7 @@
 
 # We order libraries to mirror roughly how they are layered, except that compiler-rt can depend
 # on libc++, so we put it after.
-set(LLVM_DEFAULT_RUNTIMES "libc;libunwind;libcxxabi;pstl;libcxx;compiler-rt;openmp")
+set(LLVM_DEFAULT_RUNTIMES "libc;libunwind;pstl;libcxxabi;libcxx;compiler-rt;openmp")
 set(LLVM_ALL_RUNTIMES "${LLVM_DEFAULT_RUNTIMES};llvm-libgcc")
 set(LLVM_ENABLE_RUNTIMES "" CACHE STRING
   "Semicolon-separated list of runtimes to build (${LLVM_ALL_RUNTIMES}), or \"all\".")