diff --git a/libcxx/CMakeLists.txt b/libcxx/CMakeLists.txt
--- a/libcxx/CMakeLists.txt
+++ b/libcxx/CMakeLists.txt
@@ -137,12 +137,31 @@
     are new library features under development. These features don't guarantee
     ABI stability nor the quality of completed library features. Vendors
     shipping the library may want to disable this option." ON)
-set(LIBCXX_TEST_CONFIG "legacy.cfg.in" CACHE STRING
+
+if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
+  set(LIBCXX_DEFAULT_TEST_CONFIG "llvm-libc++-shared-gcc.cfg.in")
+elseif(MINGW)
+  set(LIBCXX_DEFAULT_TEST_CONFIG "llvm-libc++-mingw.cfg.in")
+elseif(WIN32) # clang-cl
+  if (LIBCXX_ENABLE_SHARED)
+    set(LIBCXX_DEFAULT_TEST_CONFIG "llvm-libc++-shared-clangcl.cfg.in")
+  else()
+    set(LIBCXX_DEFAULT_TEST_CONFIG "llvm-libc++-static-clangcl.cfg.in")
+  endif()
+else()
+  if (LIBCXX_ENABLE_SHARED)
+    set(LIBCXX_DEFAULT_TEST_CONFIG "llvm-libc++-shared.cfg.in")
+  else()
+    set(LIBCXX_DEFAULT_TEST_CONFIG "llvm-libc++-static.cfg.in")
+  endif()
+endif()
+set(LIBCXX_TEST_CONFIG "${LIBCXX_DEFAULT_TEST_CONFIG}" CACHE STRING
     "The path to the Lit testing configuration to use when running the tests.
      If a relative path is provided, it is assumed to be relative to '<monorepo>/libcxx/test/configs'.")
 if (NOT IS_ABSOLUTE "${LIBCXX_TEST_CONFIG}")
   set(LIBCXX_TEST_CONFIG "${CMAKE_CURRENT_SOURCE_DIR}/test/configs/${LIBCXX_TEST_CONFIG}")
 endif()
+message(STATUS "Using libc++ testing configuration: ${LIBCXX_TEST_CONFIG}")
 set(LIBCXX_TEST_PARAMS "" CACHE STRING
     "A list of parameters to run the Lit test suite with.")
 
diff --git a/libcxx/docs/ReleaseNotes.rst b/libcxx/docs/ReleaseNotes.rst
--- a/libcxx/docs/ReleaseNotes.rst
+++ b/libcxx/docs/ReleaseNotes.rst
@@ -98,3 +98,9 @@
   library should set ``LIBCXXABI_HERMETIC_STATIC_LIBRARY=ON`` when configuring CMake. The current
   behavior, which tries to guess the correct dll-export semantics based on whether we're building
   the libc++ shared library, will be removed in LLVM 16.
+
+- The legacy testing configuration is now deprecated and will be removed in the next release. For
+  most users, this should not have any impact. However, if you are testing libc++ in a configuration
+  or on a platform that used to be supported by the legacy testing configuration and isn't supported
+  by one of the configurations in ``libcxx/test/configs``, please reach out to the libc++ developers
+  to get your configuration supported officially.
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
@@ -192,7 +192,6 @@
 generic-cxx03)
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-cxx03.cmake" \
-                   -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
     check-abi-list
@@ -200,7 +199,6 @@
 generic-cxx11)
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-cxx11.cmake" \
-                   -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
     check-abi-list
@@ -208,7 +206,6 @@
 generic-cxx14)
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-cxx14.cmake" \
-                   -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
     check-abi-list
@@ -216,7 +213,6 @@
 generic-cxx17)
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-cxx17.cmake" \
-                   -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
     check-abi-list
@@ -224,7 +220,6 @@
 generic-cxx20)
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-cxx20.cmake" \
-                   -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
     check-abi-list
@@ -232,7 +227,6 @@
 generic-cxx2b)
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-cxx2b.cmake" \
-                   -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
     check-abi-list
@@ -240,7 +234,6 @@
 generic-assertions)
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-assertions.cmake" \
-                   -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
     check-abi-list
@@ -248,7 +241,6 @@
 generic-debug-iterators)
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-debug-iterators.cmake" \
-                   -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
     check-abi-list
@@ -256,7 +248,6 @@
 generic-noexceptions)
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-noexceptions.cmake" \
-                   -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
     check-abi-list
@@ -264,7 +255,6 @@
 generic-modules)
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-modules.cmake" \
-                   -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
     check-abi-list
@@ -272,7 +262,6 @@
 generic-static)
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-static.cmake" \
-                   -DLIBCXX_TEST_CONFIG="llvm-libc++-static.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-static.cfg.in"
     check-runtimes
 ;;
@@ -280,8 +269,7 @@
     export CC=clang-13
     export CXX=clang++-13
     clean
-    generate-cmake -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
-                   -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
+    generate-cmake -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
     check-abi-list
 ;;
@@ -289,8 +277,7 @@
     export CC=clang-14
     export CXX=clang++-14
     clean
-    generate-cmake -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
-                   -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
+    generate-cmake -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
     check-abi-list
 ;;
@@ -298,8 +285,7 @@
     export CC=gcc-11
     export CXX=g++-11
     clean
-    generate-cmake -DLIBCXX_TEST_CONFIG="llvm-libc++-shared-gcc.cfg.in" \
-                   -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in" \
+    generate-cmake -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in" \
                    -DLIBCXX_ENABLE_WERROR=NO
     check-runtimes
 ;;
@@ -308,7 +294,6 @@
     export CXX=g++-11
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-cxx11.cmake" \
-                   -DLIBCXX_TEST_CONFIG="llvm-libc++-shared-gcc.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in" \
                    -DLIBCXX_ENABLE_WERROR=NO
     check-runtimes
@@ -316,49 +301,42 @@
 generic-asan)
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-asan.cmake" \
-                   -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
 ;;
 generic-msan)
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-msan.cmake" \
-                   -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
 ;;
 generic-tsan)
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-tsan.cmake" \
-                   -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
 ;;
 generic-ubsan)
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-ubsan.cmake" \
-                   -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
 ;;
 generic-with_llvm_unwinder)
     clean
     generate-cmake -DLIBCXXABI_USE_LLVM_UNWINDER=ON \
-                   -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
 ;;
 generic-singlethreaded)
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-singlethreaded.cmake" \
-                   -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
 ;;
 generic-no-debug)
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-no-debug.cmake" \
-                   -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
     check-abi-list
@@ -366,42 +344,36 @@
 generic-no-filesystem)
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-no-filesystem.cmake" \
-                   -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
 ;;
 generic-no-random_device)
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-no-random_device.cmake" \
-                   -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
 ;;
 generic-no-localization)
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-no-localization.cmake" \
-                   -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
 ;;
 generic-no-unicode)
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-no-unicode.cmake" \
-                   -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
 ;;
 generic-no-wide-characters)
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-no-wide-characters.cmake" \
-                   -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
 ;;
 generic-no-experimental)
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-no-experimental.cmake" \
-                   -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
     check-abi-list
@@ -409,7 +381,6 @@
 generic-abi-unstable)
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-abi-unstable.cmake" \
-                   -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
 ;;
@@ -465,8 +436,7 @@
 ;;
 benchmarks)
     clean
-    generate-cmake -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
-                   -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
+    generate-cmake -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-cxx-benchmarks
 ;;
 documentation)
@@ -497,7 +467,6 @@
           -DRUNTIMES_BUILD_ALLOW_DARWIN=ON \
           -DLLVM_ENABLE_ASSERTIONS=ON \
           -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-modules.cmake" \
-          -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
           -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
 
     echo "+++ Running the libc++ and libc++abi tests"
@@ -529,7 +498,6 @@
 aarch64)
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/AArch64.cmake" \
-                   -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
 ;;
@@ -538,7 +506,6 @@
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/AArch64.cmake" \
                    -DLIBCXX_ENABLE_EXCEPTIONS=OFF \
                    -DLIBCXXABI_ENABLE_EXCEPTIONS=OFF \
-                   -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
 ;;
@@ -546,14 +513,12 @@
 armv8)
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Armv8Arm.cmake" \
-                   -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
 ;;
 armv8-noexceptions)
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Armv8Thumb-noexceptions.cmake" \
-                   -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
 ;;
@@ -561,14 +526,12 @@
 armv7)
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Armv7Arm.cmake" \
-                   -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
 ;;
 armv7-noexceptions)
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Armv7Thumb-noexceptions.cmake" \
-                   -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
 ;;
@@ -580,15 +543,13 @@
     # correctly when libc++ visibility attributes indicate dllimport linkage
     # anyway), thus just disable the experimental library. Remove this
     # setting when cmake and the test driver does the right thing automatically.
-    generate-cmake-libcxx-win -DLIBCXX_ENABLE_EXPERIMENTAL_LIBRARY=OFF \
-                              -DLIBCXX_TEST_CONFIG="llvm-libc++-shared-clangcl.cfg.in"
+    generate-cmake-libcxx-win -DLIBCXX_ENABLE_EXPERIMENTAL_LIBRARY=OFF
     echo "+++ Running the libc++ tests"
     ${NINJA} -vC "${BUILD_DIR}" check-cxx
 ;;
 clang-cl-static)
     clean
-    generate-cmake-libcxx-win -DLIBCXX_ENABLE_SHARED=OFF \
-                              -DLIBCXX_TEST_CONFIG="llvm-libc++-static-clangcl.cfg.in"
+    generate-cmake-libcxx-win -DLIBCXX_ENABLE_SHARED=OFF
     echo "+++ Running the libc++ tests"
     ${NINJA} -vC "${BUILD_DIR}" check-cxx
 ;;
@@ -602,7 +563,6 @@
     generate-cmake \
           -DCMAKE_C_COMPILER=x86_64-w64-mingw32-clang \
           -DCMAKE_CXX_COMPILER=x86_64-w64-mingw32-clang++ \
-          -DLIBCXX_TEST_CONFIG="llvm-libc++-mingw.cfg.in" \
           -C "${MONOREPO_ROOT}/libcxx/cmake/caches/MinGW.cmake"
     echo "+++ Running the libc++ tests"
     ${NINJA} -vC "${BUILD_DIR}" check-cxx
@@ -612,7 +572,6 @@
     generate-cmake \
           -DCMAKE_C_COMPILER=x86_64-w64-mingw32-clang \
           -DCMAKE_CXX_COMPILER=x86_64-w64-mingw32-clang++ \
-          -DLIBCXX_TEST_CONFIG="llvm-libc++-mingw.cfg.in" \
           -C "${MONOREPO_ROOT}/libcxx/cmake/caches/MinGW.cmake" \
           -DLIBCXX_ENABLE_SHARED=OFF \
           -DLIBUNWIND_ENABLE_SHARED=OFF