diff --git a/libcxx/cmake/caches/AndroidNDK.cmake b/libcxx/cmake/caches/AndroidNDK.cmake
new file mode 100644
--- /dev/null
+++ b/libcxx/cmake/caches/AndroidNDK.cmake
@@ -0,0 +1,38 @@
+# Build libc++abi and libc++ closely resembling what is shipped in the Android
+# NDK.
+
+# The NDK names the libraries libc++_shared.so and libc++_static.a. Using the
+# libc++_shared.so soname ensures that the library doesn't interact with the
+# libc++.so in /system/lib[64].
+set(LIBCXX_SHARED_OUTPUT_NAME c++_shared CACHE STRING "")
+set(LIBCXX_STATIC_OUTPUT_NAME c++_static CACHE STRING "")
+
+# The NDK libc++ uses a special namespace to help isolate its symbols from those
+# in the platform's STL (e.g. /system/lib[64]/libc++.so, but possibly stlport on
+# older versions of Android).
+set(LIBCXX_ABI_VERSION 1)
+set(LIBCXX_ABI_NAMESPACE __ndk1 CACHE STRING "")
+
+# CMake doesn't add a version suffix to an Android shared object filename,
+# (because CMAKE_PLATFORM_NO_VERSIONED_SONAME is set), so it writes both a
+# libc++_shared.so ELF file and a libc++_shared.so linker script to the same
+# output path (the script clobbers the binary). Turn off the linker script.
+set(LIBCXX_ENABLE_ABI_LINKER_SCRIPT OFF CACHE BOOL "")
+
+set(LIBCXX_STATICALLY_LINK_ABI_IN_SHARED_LIBRARY ON CACHE BOOL "")
+set(LIBCXXABI_ENABLE_SHARED OFF CACHE BOOL "")
+
+# Clang links libc++ by default, but it doesn't exist yet. The libc++ CMake
+# files specify -nostdlib++ to avoid this problem, but CMake's default "compiler
+# works" testing doesn't pass that flag, so force those tests to pass.
+set(CMAKE_C_COMPILER_WORKS ON CACHE BOOL "")
+set(CMAKE_CXX_COMPILER_WORKS ON CACHE BOOL "")
+
+# Use adb to push tests to a locally-connected device (e.g. emulator) and run
+# them.
+set(LIBCXX_TEST_CONFIG "llvm-libc++-android-ndk.cfg.in" CACHE STRING "")
+set(LIBCXXABI_TEST_CONFIG "llvm-libc++abi-android-ndk.cfg.in" CACHE STRING "")
+
+# CMAKE_SOURCE_DIR refers to the "<monorepo>/runtimes" directory.
+set(LIBCXX_EXECUTOR "${CMAKE_SOURCE_DIR}/../libcxx/utils/adb_run.py" CACHE STRING "")
+set(LIBCXXABI_EXECUTOR "${LIBCXX_EXECUTOR}" CACHE STRING "")
diff --git a/libcxx/docs/index.rst b/libcxx/docs/index.rst
--- a/libcxx/docs/index.rst
+++ b/libcxx/docs/index.rst
@@ -130,6 +130,7 @@
 macOS 10.9+     i386, x86_64, arm64       Building the shared library itself requires targetting macOS 10.13+
 FreeBSD 12+     i386, x86_64, arm
 Linux           i386, x86_64, arm, arm64  Only glibc-2.24 and later and no other libc is officially supported
+Android 5.0+    i386, x86_64, arm, arm64
 Windows         i386, x86_64              Both MSVC and MinGW style environments, ABI in MSVC environments is :doc:`unstable <DesignDocs/ABIVersioning>`
 AIX 7.2TL5+     powerpc, powerpc64
 =============== ========================= ============================
diff --git a/libcxx/test/configs/llvm-libc++-android-ndk.cfg.in b/libcxx/test/configs/llvm-libc++-android-ndk.cfg.in
new file mode 100644
--- /dev/null
+++ b/libcxx/test/configs/llvm-libc++-android-ndk.cfg.in
@@ -0,0 +1,47 @@
+# This testing configuration handles running the test suite against LLVM's
+# libc++ using adb and a libc++_shared.so library on Android.
+
+lit_config.load_config(config, '@CMAKE_CURRENT_BINARY_DIR@/cmake-bridge.cfg')
+
+import re
+import site
+
+site.addsitedir(os.path.join('@LIBCXX_SOURCE_DIR@', 'utils'))
+
+import libcxx.test.android
+import libcxx.test.config
+import libcxx.test.params
+
+config.substitutions.append(('%{flags}',
+    '--sysroot @CMAKE_SYSROOT@' if '@CMAKE_SYSROOT@' else ''
+))
+
+compile_flags = '-nostdinc++ -I %{include} -I %{target-include} -I %{libcxx}/test/support'
+if re.match(r'i686-linux-android(21|22|23)$', config.target_triple):
+    # 32-bit x86 Android has a bug where the stack is sometimes misaligned.
+    # The problem appears limited to versions before Android N (API 24) and only
+    # __attribute__((constructor)) functions. Compile with -mstackrealign to
+    # work around the bug.
+    # TODO: Consider automatically doing something like this in Clang itself (LIBCXX-ANDROID-FIXME)
+    # See https://github.com/android/ndk/issues/693.
+    compile_flags += ' -mstackrealign'
+config.substitutions.append(('%{compile_flags}', compile_flags))
+
+# The NDK library is called "libc++_shared.so". Use LD_LIBRARY_PATH to find
+# libc++_shared.so because older Bionic dynamic loaders don't support rpath
+# lookup.
+config.substitutions.append(('%{link_flags}',
+    '-nostdlib++ -L %{lib} -lc++_shared'
+))
+config.substitutions.append(('%{exec}',
+    '%{executor}' +
+    ' --job-limit-socket ' + libcxx.test.android.adb_job_limit_socket() +
+    ' --prepend-path-env LD_LIBRARY_PATH /data/local/tmp/libc++ --execdir %T -- '
+))
+
+libcxx.test.config.configure(
+    libcxx.test.params.DEFAULT_PARAMETERS,
+    libcxx.test.features.DEFAULT_FEATURES,
+    config,
+    lit_config
+)
diff --git a/libcxx/test/libcxx/clang_modules_include.gen.py b/libcxx/test/libcxx/clang_modules_include.gen.py
--- a/libcxx/test/libcxx/clang_modules_include.gen.py
+++ b/libcxx/test/libcxx/clang_modules_include.gen.py
@@ -34,7 +34,7 @@
 // UNSUPPORTED{BLOCKLIT}: LIBCXX-AIX-FIXME
 
 // The Android headers don't appear to be compatible with modules yet
-// XFAIL{BLOCKLIT}: LIBCXX-ANDROID-FIXME
+// UNSUPPORTED{BLOCKLIT}: LIBCXX-ANDROID-FIXME
 
 // TODO: Investigate this failure
 // UNSUPPORTED{BLOCKLIT}: LIBCXX-FREEBSD-FIXME
@@ -64,7 +64,7 @@
 // UNSUPPORTED{BLOCKLIT}: LIBCXX-AIX-FIXME
 
 // The Android headers don't appear to be compatible with modules yet
-// XFAIL{BLOCKLIT}: LIBCXX-ANDROID-FIXME
+// UNSUPPORTED{BLOCKLIT}: LIBCXX-ANDROID-FIXME
 
 // TODO: Investigate this failure
 // UNSUPPORTED{BLOCKLIT}: LIBCXX-FREEBSD-FIXME
diff --git a/libcxx/test/libcxx/gdb/gdb_pretty_printer_test.sh.cpp b/libcxx/test/libcxx/gdb/gdb_pretty_printer_test.sh.cpp
--- a/libcxx/test/libcxx/gdb/gdb_pretty_printer_test.sh.cpp
+++ b/libcxx/test/libcxx/gdb/gdb_pretty_printer_test.sh.cpp
@@ -17,6 +17,12 @@
 // TODO: Investigate this failure on GCC 13 (in Ubuntu Jammy)
 // UNSUPPORTED: gcc-13
 
+// The Android libc++ tests are run on a non-Android host, connected to an
+// Android device over adb. gdb needs special support to make this work (e.g.
+// gdbclient.py, ndk-gdb.py, gdbserver), and the Android organization doesn't
+// support gdb anymore, favoring lldb instead.
+// UNSUPPORTED: android
+
 // RUN: %{cxx} %{flags} %s -o %t.exe %{compile_flags} -g %{link_flags}
 // Ensure locale-independence for unicode tests.
 // RUN: env LANG=en_US.UTF-8 %{gdb} -nx -batch -iex "set autoload off" -ex "source %S/../../../utils/gdb/libcxx/printers.py" -ex "python register_libcxx_printer_loader()" -ex "source %S/gdb_pretty_printer_test.py" %t.exe
diff --git a/libcxx/test/libcxx/input.output/iostream.format/print.fun/vprint_unicode_posix.pass.cpp b/libcxx/test/libcxx/input.output/iostream.format/print.fun/vprint_unicode_posix.pass.cpp
--- a/libcxx/test/libcxx/input.output/iostream.format/print.fun/vprint_unicode_posix.pass.cpp
+++ b/libcxx/test/libcxx/input.output/iostream.format/print.fun/vprint_unicode_posix.pass.cpp
@@ -11,6 +11,9 @@
 
 // XFAIL: availability-fp_to_chars-missing
 
+// fmemopen is available starting in Android M (API 23)
+// XFAIL: target={{.+}}-android{{(eabi)?(21|22)}}
+
 // REQUIRES: has-unix-headers
 
 // <print>
diff --git a/libcxx/test/std/input.output/file.streams/fstreams/filebuf.members/close.pass.cpp b/libcxx/test/std/input.output/file.streams/fstreams/filebuf.members/close.pass.cpp
--- a/libcxx/test/std/input.output/file.streams/fstreams/filebuf.members/close.pass.cpp
+++ b/libcxx/test/std/input.output/file.streams/fstreams/filebuf.members/close.pass.cpp
@@ -10,6 +10,11 @@
 
 // basic_filebuf<charT,traits>* close();
 
+// This test closes an fd that belongs to a std::filebuf, and Bionic's fdsan
+// detects this and aborts the process, starting in Android R (API 30).
+// See D137129.
+// XFAIL: LIBCXX-ANDROID-FIXME && !android-device-api={{2[1-9]}}
+
 #include <fstream>
 #include <cassert>
 #if defined(__unix__)
diff --git a/libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.obs/file_size.pass.cpp b/libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.obs/file_size.pass.cpp
--- a/libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.obs/file_size.pass.cpp
+++ b/libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.obs/file_size.pass.cpp
@@ -12,6 +12,10 @@
 // against already-released libc++'s.
 // XFAIL: stdlib=apple-libc++ && target={{.+}}-apple-macosx{{10.15|11.0}}
 
+// Starting in Android N (API 24), SELinux policy prevents the shell user from
+// creating a FIFO file.
+// XFAIL: LIBCXX-ANDROID-FIXME && !android-device-api={{21|22|23}}
+
 // <filesystem>
 
 // class directory_entry
diff --git a/libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.obs/file_type_obs.pass.cpp b/libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.obs/file_type_obs.pass.cpp
--- a/libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.obs/file_type_obs.pass.cpp
+++ b/libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.obs/file_type_obs.pass.cpp
@@ -8,6 +8,10 @@
 
 // UNSUPPORTED: c++03
 
+// Starting in Android N (API 24), SELinux policy prevents the shell user from
+// creating a hard link.
+// XFAIL: LIBCXX-ANDROID-FIXME && !android-device-api={{21|22|23}}
+
 // <filesystem>
 
 // class directory_entry
diff --git a/libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.obs/hard_link_count.pass.cpp b/libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.obs/hard_link_count.pass.cpp
--- a/libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.obs/hard_link_count.pass.cpp
+++ b/libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.obs/hard_link_count.pass.cpp
@@ -12,6 +12,10 @@
 // against already-released libc++'s.
 // XFAIL: stdlib=apple-libc++ && target={{.+}}-apple-macosx{{10.15|11.0}}
 
+// Starting in Android N (API 24), SELinux policy prevents the shell user from
+// creating a hard link.
+// XFAIL: LIBCXX-ANDROID-FIXME && !android-device-api={{21|22|23}}
+
 // <filesystem>
 
 // class directory_entry
diff --git a/libcxx/test/std/input.output/filesystems/class.rec.dir.itr/rec.dir.itr.members/increment.pass.cpp b/libcxx/test/std/input.output/filesystems/class.rec.dir.itr/rec.dir.itr.members/increment.pass.cpp
--- a/libcxx/test/std/input.output/filesystems/class.rec.dir.itr/rec.dir.itr.members/increment.pass.cpp
+++ b/libcxx/test/std/input.output/filesystems/class.rec.dir.itr/rec.dir.itr.members/increment.pass.cpp
@@ -10,6 +10,10 @@
 // UNSUPPORTED: no-filesystem
 // UNSUPPORTED: availability-filesystem-missing
 
+// On Android L, ~scoped_test_env() is unable to delete the temp dir using
+// chmod+rm because chmod is too broken.
+// XFAIL: LIBCXX-ANDROID-FIXME && android-device-api={{21|22}}
+
 // <filesystem>
 
 // class recursive_directory_iterator
diff --git a/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.hard_lk_ct/hard_link_count.pass.cpp b/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.hard_lk_ct/hard_link_count.pass.cpp
--- a/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.hard_lk_ct/hard_link_count.pass.cpp
+++ b/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.hard_lk_ct/hard_link_count.pass.cpp
@@ -10,6 +10,10 @@
 // UNSUPPORTED: no-filesystem
 // UNSUPPORTED: availability-filesystem-missing
 
+// Starting in Android N (API 24), SELinux policy prevents the shell user from
+// creating a hard link.
+// XFAIL: LIBCXX-ANDROID-FIXME && !android-device-api={{21|22|23}}
+
 // <filesystem>
 
 // uintmax_t hard_link_count(const path& p);
diff --git a/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.copy/copy.pass.cpp b/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.copy/copy.pass.cpp
--- a/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.copy/copy.pass.cpp
+++ b/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.copy/copy.pass.cpp
@@ -10,6 +10,10 @@
 // UNSUPPORTED: no-filesystem
 // UNSUPPORTED: availability-filesystem-missing
 
+// Starting in Android N (API 24), SELinux policy prevents the shell user from
+// creating a FIFO file.
+// XFAIL: LIBCXX-ANDROID-FIXME && !android-device-api={{21|22|23}}
+
 // <filesystem>
 
 // void copy(const path& from, const path& to);
diff --git a/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.copy_file/copy_file.pass.cpp b/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.copy_file/copy_file.pass.cpp
--- a/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.copy_file/copy_file.pass.cpp
+++ b/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.copy_file/copy_file.pass.cpp
@@ -14,6 +14,10 @@
 // against already-released libc++'s.
 // XFAIL: stdlib=apple-libc++ && target={{.+}}-apple-macosx{{10.15|11.0}}
 
+// Starting in Android N (API 24), SELinux policy prevents the shell user from
+// creating a FIFO file.
+// XFAIL: LIBCXX-ANDROID-FIXME && !android-device-api={{21|22|23}}
+
 // <filesystem>
 
 // bool copy_file(const path& from, const path& to);
diff --git a/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.create_hard_link/create_hard_link.pass.cpp b/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.create_hard_link/create_hard_link.pass.cpp
--- a/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.create_hard_link/create_hard_link.pass.cpp
+++ b/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.create_hard_link/create_hard_link.pass.cpp
@@ -10,6 +10,10 @@
 // UNSUPPORTED: no-filesystem
 // UNSUPPORTED: availability-filesystem-missing
 
+// Starting in Android N (API 24), SELinux policy prevents the shell user from
+// creating a hard link.
+// XFAIL: LIBCXX-ANDROID-FIXME && !android-device-api={{21|22|23}}
+
 // <filesystem>
 
 // void create_hard_link(const path& existing_symlink, const path& new_symlink);
diff --git a/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.equivalent/equivalent.pass.cpp b/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.equivalent/equivalent.pass.cpp
--- a/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.equivalent/equivalent.pass.cpp
+++ b/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.equivalent/equivalent.pass.cpp
@@ -10,6 +10,10 @@
 // UNSUPPORTED: no-filesystem
 // UNSUPPORTED: availability-filesystem-missing
 
+// Starting in Android N (API 24), SELinux policy prevents the shell user from
+// creating a hard link.
+// XFAIL: LIBCXX-ANDROID-FIXME && !android-device-api={{21|22|23}}
+
 // <filesystem>
 
 // bool equivalent(path const& lhs, path const& rhs);
diff --git a/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.is_empty/is_empty.pass.cpp b/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.is_empty/is_empty.pass.cpp
--- a/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.is_empty/is_empty.pass.cpp
+++ b/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.is_empty/is_empty.pass.cpp
@@ -10,6 +10,10 @@
 // UNSUPPORTED: no-filesystem
 // UNSUPPORTED: availability-filesystem-missing
 
+// Starting in Android N (API 24), SELinux policy prevents the shell user from
+// creating a FIFO file.
+// XFAIL: LIBCXX-ANDROID-FIXME && !android-device-api={{21|22|23}}
+
 // <filesystem>
 
 // bool is_empty(path const& p);
diff --git a/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.permissions/permissions.pass.cpp b/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.permissions/permissions.pass.cpp
--- a/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.permissions/permissions.pass.cpp
+++ b/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.permissions/permissions.pass.cpp
@@ -10,6 +10,11 @@
 // UNSUPPORTED: no-filesystem
 // UNSUPPORTED: availability-filesystem-missing
 
+// Android's fchmodat seems broken on various OS versions -- see D140183. This
+// test probably passes on new-enough phones (not the emulator).
+// XFAIL: LIBCXX-ANDROID-FIXME && target={{i686|x86_64}}-{{.+}}-android{{.*}}
+// XFAIL: LIBCXX-ANDROID-FIXME && android-device-api={{21|22}}
+
 // <filesystem>
 
 // void permissions(const path& p, perms prms,
diff --git a/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.status/status.pass.cpp b/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.status/status.pass.cpp
--- a/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.status/status.pass.cpp
+++ b/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.status/status.pass.cpp
@@ -10,6 +10,10 @@
 // UNSUPPORTED: no-filesystem
 // UNSUPPORTED: availability-filesystem-missing
 
+// Starting in Android N (API 24), SELinux policy prevents the shell user from
+// creating a FIFO file.
+// XFAIL: LIBCXX-ANDROID-FIXME && !android-device-api={{21|22|23}}
+
 // <filesystem>
 
 // file_status status(const path& p);
diff --git a/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.symlink_status/symlink_status.pass.cpp b/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.symlink_status/symlink_status.pass.cpp
--- a/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.symlink_status/symlink_status.pass.cpp
+++ b/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.symlink_status/symlink_status.pass.cpp
@@ -10,6 +10,10 @@
 // UNSUPPORTED: no-filesystem
 // UNSUPPORTED: availability-filesystem-missing
 
+// Starting in Android N (API 24), SELinux policy prevents the shell user from
+// creating a FIFO file.
+// XFAIL: LIBCXX-ANDROID-FIXME && !android-device-api={{21|22|23}}
+
 // <filesystem>
 
 // file_status symlink_status(const path& p);
diff --git a/libcxx/test/std/input.output/iostream.format/ext.manip/get_money.pass.cpp b/libcxx/test/std/input.output/iostream.format/ext.manip/get_money.pass.cpp
--- a/libcxx/test/std/input.output/iostream.format/ext.manip/get_money.pass.cpp
+++ b/libcxx/test/std/input.output/iostream.format/ext.manip/get_money.pass.cpp
@@ -10,6 +10,9 @@
 
 // template <class moneyT> T7 get_money(moneyT& mon, bool intl = false);
 
+// Bionic has minimal locale support, investigate this later.
+// XFAIL: LIBCXX-ANDROID-FIXME
+
 // REQUIRES: locale.en_US.UTF-8
 
 #include <iomanip>
diff --git a/libcxx/test/std/input.output/iostream.format/ext.manip/put_money.pass.cpp b/libcxx/test/std/input.output/iostream.format/ext.manip/put_money.pass.cpp
--- a/libcxx/test/std/input.output/iostream.format/ext.manip/put_money.pass.cpp
+++ b/libcxx/test/std/input.output/iostream.format/ext.manip/put_money.pass.cpp
@@ -10,6 +10,9 @@
 
 // template <class charT, class moneyT> T8 put_money(const moneyT& mon, bool intl = false);
 
+// Bionic has minimal locale support, investigate this later.
+// XFAIL: LIBCXX-ANDROID-FIXME
+
 // REQUIRES: locale.en_US.UTF-8
 
 #include <iomanip>
diff --git a/libcxx/test/std/input.output/iostream.format/print.fun/no_file_description.pass.cpp b/libcxx/test/std/input.output/iostream.format/print.fun/no_file_description.pass.cpp
--- a/libcxx/test/std/input.output/iostream.format/print.fun/no_file_description.pass.cpp
+++ b/libcxx/test/std/input.output/iostream.format/print.fun/no_file_description.pass.cpp
@@ -12,6 +12,9 @@
 // XFAIL: msvc, target={{.+}}-windows-gnu
 // XFAIL: availability-fp_to_chars-missing
 
+// fmemopen is available starting in Android M (API 23)
+// XFAIL: target={{.+}}-android{{(eabi)?(21|22)}}
+
 // <print>
 
 // The FILE returned by fmemopen does not have file descriptor.
diff --git a/libcxx/test/std/input.output/iostream.format/print.fun/print.file.pass.cpp b/libcxx/test/std/input.output/iostream.format/print.fun/print.file.pass.cpp
--- a/libcxx/test/std/input.output/iostream.format/print.fun/print.file.pass.cpp
+++ b/libcxx/test/std/input.output/iostream.format/print.fun/print.file.pass.cpp
@@ -11,6 +11,9 @@
 
 // XFAIL: availability-fp_to_chars-missing
 
+// The error exception has no system error string.
+// XFAIL: LIBCXX-ANDROID-FIXME
+
 // <print>
 
 // template<class... Args>
diff --git a/libcxx/test/std/input.output/iostream.format/print.fun/println.file.pass.cpp b/libcxx/test/std/input.output/iostream.format/print.fun/println.file.pass.cpp
--- a/libcxx/test/std/input.output/iostream.format/print.fun/println.file.pass.cpp
+++ b/libcxx/test/std/input.output/iostream.format/print.fun/println.file.pass.cpp
@@ -11,6 +11,9 @@
 
 // XFAIL: availability-fp_to_chars-missing
 
+// The error exception has no system error string.
+// XFAIL: LIBCXX-ANDROID-FIXME
+
 // <print>
 
 // template<class... Args>
diff --git a/libcxx/test/std/input.output/iostream.format/print.fun/vprint_nonunicode.file.pass.cpp b/libcxx/test/std/input.output/iostream.format/print.fun/vprint_nonunicode.file.pass.cpp
--- a/libcxx/test/std/input.output/iostream.format/print.fun/vprint_nonunicode.file.pass.cpp
+++ b/libcxx/test/std/input.output/iostream.format/print.fun/vprint_nonunicode.file.pass.cpp
@@ -16,6 +16,9 @@
 
 // XFAIL: availability-fp_to_chars-missing
 
+// The error exception has no system error string.
+// XFAIL: LIBCXX-ANDROID-FIXME
+
 // <print>
 
 // void vprint_nonunicode(FILE* stream, string_view fmt, format_args args);
diff --git a/libcxx/test/std/input.output/iostream.format/print.fun/vprint_unicode.file.pass.cpp b/libcxx/test/std/input.output/iostream.format/print.fun/vprint_unicode.file.pass.cpp
--- a/libcxx/test/std/input.output/iostream.format/print.fun/vprint_unicode.file.pass.cpp
+++ b/libcxx/test/std/input.output/iostream.format/print.fun/vprint_unicode.file.pass.cpp
@@ -17,6 +17,9 @@
 
 // XFAIL: availability-fp_to_chars-missing
 
+// The error exception has no system error string.
+// XFAIL: LIBCXX-ANDROID-FIXME
+
 // <print>
 
 // void vprint_unicode(FILE* stream, string_view fmt, format_args args);
diff --git a/libcxx/test/std/input.output/stream.buffers/streambuf/streambuf.protected/streambuf.put.area/pbump2gig.pass.cpp b/libcxx/test/std/input.output/stream.buffers/streambuf/streambuf.protected/streambuf.put.area/pbump2gig.pass.cpp
--- a/libcxx/test/std/input.output/stream.buffers/streambuf/streambuf.protected/streambuf.put.area/pbump2gig.pass.cpp
+++ b/libcxx/test/std/input.output/stream.buffers/streambuf/streambuf.protected/streambuf.put.area/pbump2gig.pass.cpp
@@ -22,9 +22,8 @@
 // UNSUPPORTED: no-exceptions
 
 // Android devices frequently don't have enough memory to run this test. Rather
-// than throw std::bad_alloc, exhausting memory tends to trigger the OOM Killer
-// and/or crash the device (killing adb, rebooting it, etc).
-// UNSUPPORTED: android
+// than throw std::bad_alloc, exhausting memory triggers the OOM Killer.
+// UNSUPPORTED: LIBCXX-ANDROID-FIXME
 
 #include <sstream>
 #include <cassert>
diff --git a/libcxx/test/std/input.output/string.streams/stringstream/stringstream.members/gcount.pass.cpp b/libcxx/test/std/input.output/string.streams/stringstream/stringstream.members/gcount.pass.cpp
--- a/libcxx/test/std/input.output/string.streams/stringstream/stringstream.members/gcount.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/stringstream/stringstream.members/gcount.pass.cpp
@@ -8,6 +8,10 @@
 
 // UNSUPPORTED: 32-bit-pointer
 
+// Android devices frequently don't have enough memory to run this test. Rather
+// than throw std::bad_alloc, exhausting memory triggers the OOM Killer.
+// UNSUPPORTED: LIBCXX-ANDROID-FIXME
+
 // Test that tellp() does not break the stringstream after INT_MAX, due to use
 // of pbump() that accept int.
 
diff --git a/libcxx/test/std/localization/locale.categories/category.collate/locale.collate.byname/compare.pass.cpp b/libcxx/test/std/localization/locale.categories/category.collate/locale.collate.byname/compare.pass.cpp
--- a/libcxx/test/std/localization/locale.categories/category.collate/locale.collate.byname/compare.pass.cpp
+++ b/libcxx/test/std/localization/locale.categories/category.collate/locale.collate.byname/compare.pass.cpp
@@ -6,6 +6,9 @@
 //
 //===----------------------------------------------------------------------===//
 
+// Bionic has minimal locale support, investigate this later.
+// XFAIL: LIBCXX-ANDROID-FIXME
+
 // REQUIRES: locale.en_US.UTF-8
 
 // <locale>
diff --git a/libcxx/test/std/localization/locale.categories/category.collate/locale.collate.byname/transform.pass.cpp b/libcxx/test/std/localization/locale.categories/category.collate/locale.collate.byname/transform.pass.cpp
--- a/libcxx/test/std/localization/locale.categories/category.collate/locale.collate.byname/transform.pass.cpp
+++ b/libcxx/test/std/localization/locale.categories/category.collate/locale.collate.byname/transform.pass.cpp
@@ -9,6 +9,9 @@
 // NetBSD does not support LC_COLLATE at the moment
 // XFAIL: netbsd
 
+// Bionic has minimal locale support, investigate this later.
+// XFAIL: LIBCXX-ANDROID-FIXME
+
 // <locale>
 
 // template <class charT> class collate_byname
diff --git a/libcxx/test/std/localization/locale.categories/category.ctype/locale.ctype.byname/is_1.pass.cpp b/libcxx/test/std/localization/locale.categories/category.ctype/locale.ctype.byname/is_1.pass.cpp
--- a/libcxx/test/std/localization/locale.categories/category.ctype/locale.ctype.byname/is_1.pass.cpp
+++ b/libcxx/test/std/localization/locale.categories/category.ctype/locale.ctype.byname/is_1.pass.cpp
@@ -15,6 +15,9 @@
 // REQUIRES: locale.en_US.UTF-8
 // XFAIL: no-wide-characters
 
+// Bionic has minimal locale support, investigate this later.
+// XFAIL: LIBCXX-ANDROID-FIXME
+
 #include <locale>
 #include <type_traits>
 #include <cassert>
diff --git a/libcxx/test/std/localization/locale.categories/category.ctype/locale.ctype.byname/is_many.pass.cpp b/libcxx/test/std/localization/locale.categories/category.ctype/locale.ctype.byname/is_many.pass.cpp
--- a/libcxx/test/std/localization/locale.categories/category.ctype/locale.ctype.byname/is_many.pass.cpp
+++ b/libcxx/test/std/localization/locale.categories/category.ctype/locale.ctype.byname/is_many.pass.cpp
@@ -15,6 +15,9 @@
 // REQUIRES: locale.en_US.UTF-8
 // XFAIL: no-wide-characters
 
+// Bionic has minimal locale support, investigate this later.
+// XFAIL: LIBCXX-ANDROID-FIXME
+
 #include <locale>
 #include <string>
 #include <vector>
diff --git a/libcxx/test/std/localization/locale.categories/category.ctype/locale.ctype.byname/scan_is.pass.cpp b/libcxx/test/std/localization/locale.categories/category.ctype/locale.ctype.byname/scan_is.pass.cpp
--- a/libcxx/test/std/localization/locale.categories/category.ctype/locale.ctype.byname/scan_is.pass.cpp
+++ b/libcxx/test/std/localization/locale.categories/category.ctype/locale.ctype.byname/scan_is.pass.cpp
@@ -15,6 +15,9 @@
 // REQUIRES: locale.en_US.UTF-8
 // XFAIL: no-wide-characters
 
+// Bionic has minimal locale support, investigate this later.
+// XFAIL: LIBCXX-ANDROID-FIXME
+
 #include <locale>
 #include <string>
 #include <vector>
diff --git a/libcxx/test/std/localization/locale.categories/category.ctype/locale.ctype.byname/scan_not.pass.cpp b/libcxx/test/std/localization/locale.categories/category.ctype/locale.ctype.byname/scan_not.pass.cpp
--- a/libcxx/test/std/localization/locale.categories/category.ctype/locale.ctype.byname/scan_not.pass.cpp
+++ b/libcxx/test/std/localization/locale.categories/category.ctype/locale.ctype.byname/scan_not.pass.cpp
@@ -15,6 +15,9 @@
 // REQUIRES: locale.en_US.UTF-8
 // XFAIL: no-wide-characters
 
+// Bionic has minimal locale support, investigate this later.
+// XFAIL: LIBCXX-ANDROID-FIXME
+
 #include <locale>
 #include <string>
 #include <vector>
diff --git a/libcxx/test/std/localization/locale.categories/category.ctype/locale.ctype.byname/tolower_1.pass.cpp b/libcxx/test/std/localization/locale.categories/category.ctype/locale.ctype.byname/tolower_1.pass.cpp
--- a/libcxx/test/std/localization/locale.categories/category.ctype/locale.ctype.byname/tolower_1.pass.cpp
+++ b/libcxx/test/std/localization/locale.categories/category.ctype/locale.ctype.byname/tolower_1.pass.cpp
@@ -9,6 +9,9 @@
 // REQUIRES: locale.en_US.UTF-8
 // XFAIL: win32-broken-utf8-wchar-ctype
 
+// Bionic has minimal locale support, investigate this later.
+// XFAIL: LIBCXX-ANDROID-FIXME
+
 // <locale>
 
 // template <class charT> class ctype_byname;
diff --git a/libcxx/test/std/localization/locale.categories/category.ctype/locale.ctype.byname/tolower_many.pass.cpp b/libcxx/test/std/localization/locale.categories/category.ctype/locale.ctype.byname/tolower_many.pass.cpp
--- a/libcxx/test/std/localization/locale.categories/category.ctype/locale.ctype.byname/tolower_many.pass.cpp
+++ b/libcxx/test/std/localization/locale.categories/category.ctype/locale.ctype.byname/tolower_many.pass.cpp
@@ -9,6 +9,9 @@
 // REQUIRES: locale.en_US.UTF-8
 // XFAIL: win32-broken-utf8-wchar-ctype
 
+// Bionic has minimal locale support, investigate this later.
+// XFAIL: LIBCXX-ANDROID-FIXME
+
 // <locale>
 
 // template <class charT> class ctype_byname;
diff --git a/libcxx/test/std/localization/locale.categories/category.ctype/locale.ctype.byname/toupper_1.pass.cpp b/libcxx/test/std/localization/locale.categories/category.ctype/locale.ctype.byname/toupper_1.pass.cpp
--- a/libcxx/test/std/localization/locale.categories/category.ctype/locale.ctype.byname/toupper_1.pass.cpp
+++ b/libcxx/test/std/localization/locale.categories/category.ctype/locale.ctype.byname/toupper_1.pass.cpp
@@ -9,6 +9,9 @@
 // REQUIRES: locale.en_US.UTF-8
 // XFAIL: win32-broken-utf8-wchar-ctype
 
+// Bionic has minimal locale support, investigate this later.
+// XFAIL: LIBCXX-ANDROID-FIXME
+
 // <locale>
 
 // template <class charT> class ctype_byname;
diff --git a/libcxx/test/std/localization/locale.categories/category.ctype/locale.ctype.byname/toupper_many.pass.cpp b/libcxx/test/std/localization/locale.categories/category.ctype/locale.ctype.byname/toupper_many.pass.cpp
--- a/libcxx/test/std/localization/locale.categories/category.ctype/locale.ctype.byname/toupper_many.pass.cpp
+++ b/libcxx/test/std/localization/locale.categories/category.ctype/locale.ctype.byname/toupper_many.pass.cpp
@@ -9,6 +9,9 @@
 // REQUIRES: locale.en_US.UTF-8
 // XFAIL: win32-broken-utf8-wchar-ctype
 
+// Bionic has minimal locale support, investigate this later.
+// XFAIL: LIBCXX-ANDROID-FIXME
+
 // <locale>
 
 // template <class charT> class ctype_byname;
diff --git a/libcxx/test/std/localization/locale.categories/category.monetary/locale.money.get/locale.money.get.members/get_long_double_en_US.pass.cpp b/libcxx/test/std/localization/locale.categories/category.monetary/locale.money.get/locale.money.get.members/get_long_double_en_US.pass.cpp
--- a/libcxx/test/std/localization/locale.categories/category.monetary/locale.money.get/locale.money.get.members/get_long_double_en_US.pass.cpp
+++ b/libcxx/test/std/localization/locale.categories/category.monetary/locale.money.get/locale.money.get.members/get_long_double_en_US.pass.cpp
@@ -13,6 +13,9 @@
 // iter_type get(iter_type b, iter_type e, bool intl, ios_base& iob,
 //               ios_base::iostate& err, long double& v) const;
 
+// Bionic has minimal locale support, investigate this later.
+// XFAIL: LIBCXX-ANDROID-FIXME
+
 // REQUIRES: locale.en_US.UTF-8
 
 #include <locale>
diff --git a/libcxx/test/std/localization/locale.categories/category.monetary/locale.money.get/locale.money.get.members/get_string_en_US.pass.cpp b/libcxx/test/std/localization/locale.categories/category.monetary/locale.money.get/locale.money.get.members/get_string_en_US.pass.cpp
--- a/libcxx/test/std/localization/locale.categories/category.monetary/locale.money.get/locale.money.get.members/get_string_en_US.pass.cpp
+++ b/libcxx/test/std/localization/locale.categories/category.monetary/locale.money.get/locale.money.get.members/get_string_en_US.pass.cpp
@@ -13,6 +13,9 @@
 // iter_type get(iter_type b, iter_type e, bool intl, ios_base& iob,
 //               ios_base::iostate& err, string_type& v) const;
 
+// Bionic has minimal locale support, investigate this later.
+// XFAIL: LIBCXX-ANDROID-FIXME
+
 // REQUIRES: locale.en_US.UTF-8
 
 #include <locale>
diff --git a/libcxx/test/std/localization/locale.categories/category.monetary/locale.money.put/locale.money.put.members/put_long_double_en_US.pass.cpp b/libcxx/test/std/localization/locale.categories/category.monetary/locale.money.put/locale.money.put.members/put_long_double_en_US.pass.cpp
--- a/libcxx/test/std/localization/locale.categories/category.monetary/locale.money.put/locale.money.put.members/put_long_double_en_US.pass.cpp
+++ b/libcxx/test/std/localization/locale.categories/category.monetary/locale.money.put/locale.money.put.members/put_long_double_en_US.pass.cpp
@@ -13,6 +13,9 @@
 // iter_type put(iter_type s, bool intl, ios_base& f, char_type fill,
 //               long double units) const;
 
+// Bionic has minimal locale support, investigate this later.
+// XFAIL: LIBCXX-ANDROID-FIXME
+
 // REQUIRES: locale.en_US.UTF-8
 
 #include <locale>
diff --git a/libcxx/test/std/localization/locale.categories/category.monetary/locale.money.put/locale.money.put.members/put_string_en_US.pass.cpp b/libcxx/test/std/localization/locale.categories/category.monetary/locale.money.put/locale.money.put.members/put_string_en_US.pass.cpp
--- a/libcxx/test/std/localization/locale.categories/category.monetary/locale.money.put/locale.money.put.members/put_string_en_US.pass.cpp
+++ b/libcxx/test/std/localization/locale.categories/category.monetary/locale.money.put/locale.money.put.members/put_string_en_US.pass.cpp
@@ -13,6 +13,9 @@
 // iter_type put(iter_type s, bool intl, ios_base& f, char_type fill,
 //               const string_type& units) const;
 
+// Bionic has minimal locale support, investigate this later.
+// XFAIL: LIBCXX-ANDROID-FIXME
+
 // REQUIRES: locale.en_US.UTF-8
 
 #include <locale>
diff --git a/libcxx/test/std/localization/locale.categories/category.numeric/locale.nm.put/facet.num.put.members/put_long_double.pass.cpp b/libcxx/test/std/localization/locale.categories/category.numeric/locale.nm.put/facet.num.put.members/put_long_double.pass.cpp
--- a/libcxx/test/std/localization/locale.categories/category.numeric/locale.nm.put/facet.num.put.members/put_long_double.pass.cpp
+++ b/libcxx/test/std/localization/locale.categories/category.numeric/locale.nm.put/facet.num.put.members/put_long_double.pass.cpp
@@ -14,6 +14,10 @@
 
 // XFAIL: win32-broken-printf-g-precision
 
+// Needs more investigation, but this is probably failing on Android M (API 23)
+// and up because the printf formatting of NAN changed.
+// XFAIL: LIBCXX-ANDROID-FIXME && !android-device-api={{21|22}}
+
 #include <locale>
 #include <ios>
 #include <cassert>
diff --git a/libcxx/test/std/re/re.traits/translate_nocase.pass.cpp b/libcxx/test/std/re/re.traits/translate_nocase.pass.cpp
--- a/libcxx/test/std/re/re.traits/translate_nocase.pass.cpp
+++ b/libcxx/test/std/re/re.traits/translate_nocase.pass.cpp
@@ -15,6 +15,10 @@
 // REQUIRES: locale.en_US.UTF-8
 // XFAIL: win32-broken-utf8-wchar-ctype
 
+// Prior to Android O (API 26), in the "en_US.UTF-8" locale, towlower(L'\xDA')
+// returned 0xDA instead of 0xFA.
+// XFAIL: LIBCXX-ANDROID-FIXME && android-device-api={{21|22|23|24|25}}
+
 #include <regex>
 #include <cassert>
 
diff --git a/libcxx/test/std/thread/thread.condition/thread.condition.condvar/notify_one.pass.cpp b/libcxx/test/std/thread/thread.condition/thread.condition.condvar/notify_one.pass.cpp
--- a/libcxx/test/std/thread/thread.condition/thread.condition.condvar/notify_one.pass.cpp
+++ b/libcxx/test/std/thread/thread.condition/thread.condition.condvar/notify_one.pass.cpp
@@ -8,6 +8,9 @@
 //
 // UNSUPPORTED: no-threads
 
+// This test occasionally fails on Android.
+// UNSUPPORTED: LIBCXX-ANDROID-FIXME
+
 // <condition_variable>
 
 // class condition_variable;
diff --git a/libcxx/test/std/utilities/format/format.functions/locale-specific_form.pass.cpp b/libcxx/test/std/utilities/format/format.functions/locale-specific_form.pass.cpp
--- a/libcxx/test/std/utilities/format/format.functions/locale-specific_form.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.functions/locale-specific_form.pass.cpp
@@ -11,6 +11,9 @@
 
 // XFAIL: availability-fp_to_chars-missing
 
+// Bionic has minimal locale support, investigate this later.
+// XFAIL: LIBCXX-ANDROID-FIXME
+
 // REQUIRES: locale.en_US.UTF-8
 
 // <format>
diff --git a/libcxx/test/support/filesystem_test_helper.h b/libcxx/test/support/filesystem_test_helper.h
--- a/libcxx/test/support/filesystem_test_helper.h
+++ b/libcxx/test/support/filesystem_test_helper.h
@@ -180,13 +180,22 @@
         std::string cmd = "chmod -R 777 " + test_root.string();
 #endif // defined(__MVS__)
         int ret = std::system(cmd.c_str());
-#if !defined(_AIX)
+#  if !defined(_AIX) && !defined(__ANDROID__)
         // On AIX the chmod command will return non-zero when trying to set
         // the permissions on a directory that contains a bad symlink. This triggers
         // the assert, despite being able to delete everything with the following
         // `rm -r` command.
+        //
+        // Android's chmod was buggy in old OSs, but skipping this assert is
+        // sufficient to ensure that the `rm -rf` succeeds for almost all tests:
+        //  - Android L: chmod aborts after one error
+        //  - Android L and M: chmod -R tries to set permissions of a symlink
+        //    target.
+        // LIBCXX-ANDROID-FIXME: Other fixes to consider: place a toybox chmod
+        // onto old devices, re-enable this assert for devices running Android N
+        // and up, rewrite this chmod+rm in C or C++.
         assert(ret == 0);
-#endif
+#  endif
 
         cmd = "rm -rf " + test_root.string();
         ret = std::system(cmd.c_str());
diff --git a/libcxx/utils/adb_run.py b/libcxx/utils/adb_run.py
new file mode 100755
--- /dev/null
+++ b/libcxx/utils/adb_run.py
@@ -0,0 +1,255 @@
+#!/usr/bin/env python3
+#===----------------------------------------------------------------------===##
+#
+# 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
+#
+#===----------------------------------------------------------------------===##
+
+"""adb_run.py is a utility for running a libc++ test program via adb.
+"""
+
+import argparse
+import hashlib
+import os
+import re
+import shlex
+import socket
+import subprocess
+import sys
+from typing import List, Optional, Tuple
+
+
+# Sync a host file /path/to/dir/file to ${REMOTE_BASE_DIR}/run-${HASH}/dir/file.
+REMOTE_BASE_DIR = "/data/local/tmp/adb_run"
+
+g_job_limit_socket = None
+g_verbose = False
+
+
+def run_adb_sync_command(command: List[str]) -> None:
+    """Run an adb command and discard the output, unless the command fails. If
+    the command fails, dump the output instead, and exit the script with
+    failure.
+    """
+    if g_verbose:
+        sys.stderr.write(f"running: {shlex.join(command)}\n")
+    proc = subprocess.run(command, universal_newlines=True,
+                          stdout=subprocess.PIPE, stderr=subprocess.STDOUT,
+                          encoding="utf-8")
+    if proc.returncode != 0:
+        # adb's stdout (e.g. for adb push) should normally be discarded, but
+        # on failure, it should be shown. Print it to stderr because it's
+        # unrelated to the test program's stdout output. A common error caught
+        # here is "No space left on device".
+        sys.stderr.write(f"{proc.stdout}\n"
+                         f"error: adb command exited with {proc.returncode}: "
+                         f"{shlex.join(command)}\n")
+        sys.exit(proc.returncode)
+
+
+def sync_test_dir(local_dir: str, remote_dir: str) -> None:
+    """Sync the libc++ test directory on the host to the remote device."""
+
+    # Optimization: The typical libc++ test directory has only a single
+    # *.tmp.exe file in it. In that case, skip the `mkdir` command, which is
+    # normally necessary because we don't know if the target directory already
+    # exists on the device.
+    local_files = os.listdir(local_dir)
+    if len(local_files) == 1:
+        local_file = os.path.join(local_dir, local_files[0])
+        remote_file = os.path.join(remote_dir, local_files[0])
+        if not os.path.islink(local_file) and os.path.isfile(local_file):
+            run_adb_sync_command(["adb", "push", "--sync", local_file,
+                                  remote_file])
+            return
+
+    assert os.path.basename(local_dir) == os.path.basename(remote_dir)
+    run_adb_sync_command(["adb", "shell", "mkdir", "-p", remote_dir])
+    run_adb_sync_command(["adb", "push", "--sync", local_dir,
+                          os.path.dirname(remote_dir)])
+
+
+def build_env_arg(env_args: List[str], prepend_path_args: List[Tuple[str, str]]) -> str:
+    components = []
+    for arg in env_args:
+        k, v = arg.split("=", 1)
+        components.append(f"export {k}={shlex.quote(v)}; ")
+    for k, v in prepend_path_args:
+        components.append(f"export {k}={shlex.quote(v)}${{{k}:+:${k}}}; ")
+    return "".join(components)
+
+
+def run_command(args: argparse.Namespace) -> int:
+    local_dir = args.execdir
+    assert local_dir.startswith("/")
+    assert not local_dir.endswith("/")
+
+    # Copy each execdir to a subdir of REMOTE_BASE_DIR. Name the directory using
+    # a hash of local_dir so that concurrent adb_run invocations don't create
+    # the same intermediate parent directory. At least `adb push` has trouble
+    # with concurrent mkdir syscalls on common parent directories. (Somehow
+    # mkdir fails with EAGAIN/EWOULDBLOCK, see internal Google bug,
+    # b/289311228.)
+    local_dir_hash = hashlib.sha1(local_dir.encode()).hexdigest()
+    remote_dir = f"{REMOTE_BASE_DIR}/run-{local_dir_hash}/{os.path.basename(local_dir)}"
+    sync_test_dir(local_dir, remote_dir)
+
+    adb_shell_command = (
+        # Set the environment early so that PATH can be overridden. Overriding
+        # PATH is useful for:
+        #  - Replacing older shell utilities with toybox (e.g. on old devices).
+        #  - Adding a `bash` command that delegates to `sh` (mksh).
+        f"{build_env_arg(args.env, args.prepend_path_env)}"
+
+        # Set a high oom_score_adj so that, if the test program uses too much
+        # memory, it is killed before anything else on the device. The default
+        # oom_score_adj is -1000, so a test using too much memory typically
+        # crashes the device.
+        "echo 1000 >/proc/self/oom_score_adj; "
+
+        # If we're running as root, switch to the shell user. The libc++
+        # filesystem tests require running without root permissions. Some x86
+        # emulator devices (before Android N) do not have a working `adb unroot`
+        # and always run as root. Non-debug builds typically lack `su` and only
+        # run as the shell user.
+        #
+        # Some libc++ tests create temporary files in the working directory,
+        # which might be owned by root. Before switching to shell, make the
+        # cwd writable (and readable+executable) to every user.
+        #
+        # N.B.:
+        #  - Avoid "id -u" because it wasn't supported until Android M.
+        #  - The `env` and `which` commands were also added in Android M.
+        #  - Starting in Android M, su from root->shell resets PATH, so we need
+        #    to modify it again in the new environment.
+        #  - Avoid chmod's "a+rwx" syntax because it's not supported until
+        #    Android N.
+        #  - Defining this function allows specifying the arguments to the test
+        #    program (i.e. "$@") only once.
+        "run_without_root() {"
+        "  chmod 777 .;"
+        "  case \"$(id)\" in"
+        "    *\"uid=0(root)\"*)"
+        "    if command -v env >/dev/null; then"
+        "      su shell \"$(command -v env)\" PATH=\"$PATH\" \"$@\";"
+        "    else"
+        "      su shell \"$@\";"
+        "    fi;;"
+        "    *) \"$@\";;"
+        "  esac;"
+        "}; "
+    )
+
+    # Older versions of Bionic limit the length of argv[0] to 127 bytes
+    # (SOINFO_NAME_LEN-1), and the path to libc++ tests tend to exceed this
+    # limit. Changing the working directory works around this limit. The limit
+    # is increased to 4095 (PATH_MAX-1) in Android M (API 23).
+    command_line = [arg.replace(local_dir + "/", "./") for arg in args.command]
+
+    # Prior to the adb feature "shell_v2" (added in Android N), `adb shell`
+    # always created a pty:
+    #  - This merged stdout and stderr together.
+    #  - The pty converts LF to CRLF.
+    #  - The exit code of the shell command wasn't propagated.
+    # Work around all three limitations, unless "shell_v2" is present.
+    proc = subprocess.run(["adb", "features"], check=True,
+                          stdout=subprocess.PIPE, encoding="utf-8")
+    adb_features = set(proc.stdout.strip().split())
+    has_shell_v2 = "shell_v2" in adb_features
+    if has_shell_v2:
+        adb_shell_command += (
+            f"cd {remote_dir} && run_without_root {shlex.join(command_line)}"
+        )
+    else:
+        adb_shell_command += (
+            f"{{"
+            f"  stdout=$("
+            f"    cd {remote_dir} && run_without_root {shlex.join(command_line)};"
+            f"    echo -n __libcxx_adb_exit__=$?"
+            f"  ); "
+            f"}} 2>&1; "
+            f"echo -n __libcxx_adb_stdout__\"$stdout\""
+        )
+
+    adb_command_line = ["adb", "shell", adb_shell_command]
+    if g_verbose:
+        sys.stderr.write(f"running: {shlex.join(adb_command_line)}\n")
+
+    if has_shell_v2:
+        proc = subprocess.run(adb_command_line, shell=False, check=False,
+                              encoding="utf-8")
+        return proc.returncode
+    else:
+        proc = subprocess.run(adb_command_line, shell=False, check=False,
+                              stdout=subprocess.PIPE, stderr=subprocess.STDOUT,
+                              encoding="utf-8")
+        # The old `adb shell` mode used a pty, which converted LF to CRLF.
+        # Convert it back.
+        output = proc.stdout.replace("\r\n", "\n")
+
+        if proc.returncode:
+            sys.stderr.write(f"error: adb failed:\n"
+                             f"  command: {shlex.join(adb_command_line)}\n"
+                             f"  output: {output}\n")
+            return proc.returncode
+
+        match = re.match(r"(.*)__libcxx_adb_stdout__(.*)__libcxx_adb_exit__=(\d+)$",
+                     output, re.DOTALL)
+        if not match:
+            sys.stderr.write(f"error: could not parse adb output:\n"
+                             f"  command: {shlex.join(adb_command_line)}\n"
+                             f"  output: {output}\n")
+            return 1
+
+        sys.stderr.write(match.group(1))
+        sys.stdout.write(match.group(2))
+        return int(match.group(3))
+
+
+def connect_to_job_limiter_server(sock_addr: str) -> None:
+    sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+
+    try:
+        sock.connect(sock_addr)
+    except (FileNotFoundError, ConnectionRefusedError) as e:
+        # Copying-and-pasting an adb_run.py command-line from a lit test failure
+        # is likely to fail because the socket no longer exists (or is
+        # inactive), so just give a warning.
+        sys.stderr.write(f"warning: could not connect to {sock_addr}: {e}\n")
+        return
+
+    # The connect call can succeed before the server has called accept, because
+    # of the listen backlog, so wait for the server to send a byte.
+    sock.recv(1)
+
+    # Keep the socket open until this process ends, then let the OS close the
+    # connection automatically.
+    global g_job_limit_socket
+    g_job_limit_socket = sock
+
+
+def main() -> int:
+    """Main function (pylint wants this docstring)."""
+    parser = argparse.ArgumentParser()
+    parser.add_argument("--execdir", type=str, required=True)
+    parser.add_argument("--env", type=str, required=False, action="append",
+                        default=[], metavar="NAME=VALUE")
+    parser.add_argument("--prepend-path-env", type=str, nargs=2, required=False,
+                        action="append", default=[],
+                        metavar=("NAME", "PATH"))
+    parser.add_argument("--job-limit-socket")
+    parser.add_argument("--verbose", "-v", default=False, action="store_true")
+    parser.add_argument("command", nargs=argparse.ONE_OR_MORE)
+    args = parser.parse_args()
+
+    global g_verbose
+    g_verbose = args.verbose
+    if args.job_limit_socket is not None:
+        connect_to_job_limiter_server(args.job_limit_socket)
+    return run_command(args)
+
+
+if __name__ == '__main__':
+    sys.exit(main())
diff --git a/libcxx/utils/ci/BOT_OWNERS.txt b/libcxx/utils/ci/BOT_OWNERS.txt
--- a/libcxx/utils/ci/BOT_OWNERS.txt
+++ b/libcxx/utils/ci/BOT_OWNERS.txt
@@ -15,3 +15,8 @@
 N: LLVM on Power
 E: powerllvm@ca.ibm.com
 D: AIX, ppc64le
+
+N: Android libc++
+E: rprichard@google.com
+H: rprichard
+D: Emulator-based x86[-64] libc++ CI testing
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
@@ -1135,3 +1135,33 @@
           - exit_status: -1  # Agent was lost
             limit: 2
       timeout_in_minutes: 120
+
+  - group: ":android: Android"
+    steps:
+    - label: "Android 5.0, x86 NDK"
+      command: "libcxx/utils/ci/run-buildbot android-ndk-21-def-x86"
+      artifact_paths:
+        - "**/test-results.xml"
+        - "**/*.abilist"
+      agents:
+        queue: "libcxx-builders"
+        os: "android"
+      retry:
+        automatic:
+          - exit_status: -1  # Agent was lost
+            limit: 2
+      timeout_in_minutes: 120
+
+    - label: "Android 13, x86_64 NDK"
+      command: "libcxx/utils/ci/run-buildbot android-ndk-33-goog-x86_64"
+      artifact_paths:
+        - "**/test-results.xml"
+        - "**/*.abilist"
+      agents:
+        queue: "libcxx-builders"
+        os: "android"
+      retry:
+        automatic:
+          - exit_status: -1  # Agent was lost
+            limit: 2
+      timeout_in_minutes: 120
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
@@ -156,6 +156,13 @@
           "${@}"
 }
 
+function generate-cmake-android() {
+    generate-cmake-base \
+          -DLLVM_ENABLE_RUNTIMES="libcxx;libcxxabi" \
+          -DLIBCXX_CXX_ABI=libcxxabi \
+          "${@}"
+}
+
 function check-runtimes() {
     echo "+++ Running the libc++ tests"
     ${NINJA} -vC "${BUILD_DIR}" check-cxx
@@ -701,6 +708,49 @@
     check-abi-list
     check-runtimes
 ;;
+android-ndk-*)
+    clean
+
+    ANDROID_EMU_IMG="${BUILDER#android-ndk-}"
+    . "${MONOREPO_ROOT}/libcxx/utils/ci/vendor/android/emulator-functions.sh"
+    if ! validate_emu_img "${ANDROID_EMU_IMG}"; then
+        echo "error: android-ndk suffix must be a valid emulator image (${ANDROID_EMU_IMG})" >&2
+        exit 1
+    fi
+    ARCH=$(arch_of_emu_img ${ANDROID_EMU_IMG})
+
+    # Use the Android compiler by default.
+    export CC=${CC:-/opt/android/clang/clang-current/bin/clang}
+    export CXX=${CXX:-/opt/android/clang/clang-current/bin/clang++}
+
+    # The NDK libc++_shared.so is always built against the oldest supported API
+    # level. When tests are run against a device with a newer API level, test
+    # programs can be built for any supported API level, but building for the
+    # newest API (i.e. the system image's API) is probably the most interesting.
+    PARAMS="target_triple=$(triple_of_arch ${ARCH})$(api_of_emu_img ${ANDROID_EMU_IMG})"
+    generate-cmake-android -C "${MONOREPO_ROOT}/runtimes/cmake/android/Arch-${ARCH}.cmake" \
+                           -C "${MONOREPO_ROOT}/libcxx/cmake/caches/AndroidNDK.cmake" \
+                           -DCMAKE_SYSROOT=/opt/android/ndk/sysroot \
+                           -DLIBCXX_TEST_PARAMS="${PARAMS}" \
+                           -DLIBCXXABI_TEST_PARAMS="${PARAMS}"
+    check-abi-list
+    ${NINJA} -vC "${BUILD_DIR}" install-cxx install-cxxabi
+
+    # Start the emulator and make sure we can connect to the adb server running
+    # inside of it.
+    "${MONOREPO_ROOT}/libcxx/utils/ci/vendor/android/start-emulator.sh" ${ANDROID_EMU_IMG}
+    trap "${MONOREPO_ROOT}/libcxx/utils/ci/vendor/android/stop-emulator.sh" EXIT
+    . "${MONOREPO_ROOT}/libcxx/utils/ci/vendor/android/setup-env-for-emulator.sh"
+
+    # Create adb_run early to avoid concurrent `mkdir -p` of common parent
+    # directories.
+    adb shell mkdir -p /data/local/tmp/adb_run
+    adb push "${BUILD_DIR}/lib/libc++_shared.so" /data/local/tmp/libc++/libc++_shared.so
+    echo "+++ Running the libc++ tests"
+    ${NINJA} -vC "${BUILD_DIR}" check-cxx
+    echo "+++ Running the libc++abi tests"
+    ${NINJA} -vC "${BUILD_DIR}" check-cxxabi
+;;
 #################################################################
 # Insert vendor-specific internal configurations below.
 #
diff --git a/libcxx/utils/ci/vendor/android/Dockerfile.emulator b/libcxx/utils/ci/vendor/android/Dockerfile.emulator
new file mode 100644
--- /dev/null
+++ b/libcxx/utils/ci/vendor/android/Dockerfile.emulator
@@ -0,0 +1,59 @@
+#===----------------------------------------------------------------------===##
+#
+# 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
+#
+#===----------------------------------------------------------------------===##
+
+FROM ubuntu:jammy
+
+RUN apt-get update && apt-get install -y \
+    curl \
+    netcat-openbsd \
+    openjdk-11-jdk \
+    sudo \
+    unzip \
+    && rm -rf /var/lib/apt/lists/*
+
+ENV ANDROID_HOME /opt/android/sdk
+
+RUN curl -sL https://dl.google.com/android/repository/commandlinetools-linux-9477386_latest.zip -o cmdline-tools.zip && \
+    mkdir -p ${ANDROID_HOME} && \
+    unzip cmdline-tools.zip -d ${ANDROID_HOME}/cmdline-tools && \
+    mv ${ANDROID_HOME}/cmdline-tools/cmdline-tools ${ANDROID_HOME}/cmdline-tools/latest && \
+    rm cmdline-tools.zip
+ENV PATH="${ANDROID_HOME}/cmdline-tools/latest/bin:${PATH}"
+
+RUN yes | sdkmanager --licenses
+RUN sdkmanager --install emulator
+ENV PATH="${ANDROID_HOME}/emulator:${PATH}"
+
+ARG API  # e.g. 21
+RUN sdkmanager --install "platforms;android-${API}"
+
+ARG TYPE  # one of: default, google_apis, or google_apis_playstore
+ARG ABI   # e.g. armeabi-v7a, x86
+ENV EMU_PACKAGE_NAME="system-images;android-${API};${TYPE};${ABI}"
+RUN sdkmanager --install "${EMU_PACKAGE_NAME}"
+
+COPY ./emulator-entrypoint.sh /opt/emulator/bin/emulator-entrypoint.sh
+COPY ./emulator-wait-for-ready.sh /opt/emulator/bin/emulator-wait-for-ready.sh
+ENV PATH="/opt/emulator/bin:${PATH}"
+ENV PATH="${ANDROID_HOME}/platform-tools:${PATH}"
+
+# Setup password-less sudo so that /dev/kvm permissions can be changed. Run the
+# emulator in an unprivileged user for reliability (and it might require it?)
+RUN echo "ALL ALL = (ALL) NOPASSWD: ALL" >> /etc/sudoers
+RUN useradd --create-home emulator
+USER emulator
+WORKDIR /home/emulator
+
+# Size of emulator /data partition in megabytes.
+ENV EMU_PARTITION_SIZE=8192
+
+EXPOSE 5037
+
+HEALTHCHECK CMD emulator-wait-for-ready.sh 5
+
+ENTRYPOINT ["emulator-entrypoint.sh"]
diff --git a/libcxx/utils/ci/vendor/android/build-emulator-images.sh b/libcxx/utils/ci/vendor/android/build-emulator-images.sh
new file mode 100755
--- /dev/null
+++ b/libcxx/utils/ci/vendor/android/build-emulator-images.sh
@@ -0,0 +1,28 @@
+#!/usr/bin/env bash
+#===----------------------------------------------------------------------===##
+#
+# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+# See https://llvm.org/LICENSE.txt for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+#
+#===----------------------------------------------------------------------===##
+
+set -e
+
+THIS_DIR="$(cd "$(dirname "$0")" && pwd)"
+. "${THIS_DIR}/emulator-functions.sh"
+
+build_image() {
+    local EMU_IMG="$1"
+    validate_emu_img_syntax "${EMU_IMG}"
+    docker build -t $(docker_image_of_emu_img ${EMU_IMG}) \
+        -f Dockerfile.emulator . \
+        --build-arg API=$(api_of_emu_img ${EMU_IMG}) \
+        --build-arg TYPE=$(type_of_emu_img ${EMU_IMG}) \
+        --build-arg ABI=$(abi_of_arch $(arch_of_emu_img ${EMU_IMG}))
+}
+
+cd "${THIS_DIR}"
+
+build_image 21-def-x86
+build_image 33-goog-x86_64
diff --git a/libcxx/utils/ci/vendor/android/emulator-entrypoint.sh b/libcxx/utils/ci/vendor/android/emulator-entrypoint.sh
new file mode 100755
--- /dev/null
+++ b/libcxx/utils/ci/vendor/android/emulator-entrypoint.sh
@@ -0,0 +1,49 @@
+#!/usr/bin/env bash
+#===----------------------------------------------------------------------===##
+#
+# 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
+#
+#===----------------------------------------------------------------------===##
+
+# This script is the entrypoint of an Android Emulator Docker container.
+
+set -e
+
+# The container's /dev/kvm has the same UID+GID as the host device. Changing the
+# ownership inside the container doesn't affect the UID+GID on the host.
+sudo chown emulator:emulator /dev/kvm
+
+# Always use a copy of platform-tools provided by the host to ensure that the
+# versions of adb match between the host and the emulator.
+if [ ! -x /mnt/android-platform-tools/platform-tools/adb ]; then
+    echo "error: This image requires platform-tools mounted at" \
+         "/mnt/android-platform-tools containing platform-tools/adb" >&2
+    exit 1
+fi
+sudo cp -r /mnt/android-platform-tools/platform-tools /opt/android/sdk
+
+# Start an adb host server. `adb start-server` blocks until the port is ready.
+# Use ADB_REJECT_KILL_SERVER=1 to ensure that an adb protocol version mismatch
+# doesn't kill the adb server.
+ADB_REJECT_KILL_SERVER=1 adb -a start-server
+
+# This syntax (using an IP address of 127.0.0.1 rather than localhost) seems to
+# prevent the adb client from ever spawning an adb host server.
+export ADB_SERVER_SOCKET=tcp:127.0.0.1:5037
+
+# The AVD could already exist if the Docker container were stopped and then
+# restarted.
+if [ ! -d ~/.android/avd/emulator.avd ]; then
+    # N.B. AVD creation takes a few seconds and creates a mostly-empty
+    # multi-gigabyte userdata disk image. (It's not useful to create the AVDs in
+    # advance.)
+    avdmanager --verbose create avd --name emulator \
+        --package "${EMU_PACKAGE_NAME}" --device pixel_5
+fi
+
+# Use exec so that the emulator is PID 1, so that `docker stop` kills the
+# emulator.
+exec emulator @emulator -no-audio -no-window \
+    -partition-size "${EMU_PARTITION_SIZE}"
diff --git a/libcxx/utils/ci/vendor/android/emulator-functions.sh b/libcxx/utils/ci/vendor/android/emulator-functions.sh
new file mode 100644
--- /dev/null
+++ b/libcxx/utils/ci/vendor/android/emulator-functions.sh
@@ -0,0 +1,110 @@
+#===----------------------------------------------------------------------===##
+#
+# 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
+#
+#===----------------------------------------------------------------------===##
+
+# Bash functions for managing the names of emulator system images.
+
+# Parse the image name and set variables: API, TYPE, and ARCH.
+__parse_emu_img() {
+    if [[ "${1}" =~ ([0-9]+)-(def|goog|play)-(arm|arm64|x86|x86_64)$ ]]; then
+        API=${BASH_REMATCH[1]}
+        case ${BASH_REMATCH[2]} in
+            def) TYPE=default ;;
+            goog) TYPE=google_apis ;;
+            play) TYPE=google_apis_playstore ;;
+        esac
+        ARCH=${BASH_REMATCH[3]}
+        return 0
+    else
+        return 1
+    fi
+}
+
+# Check that the emulator image name has valid syntax.
+validate_emu_img_syntax() {
+    local EMU_IMG="${1}"
+    local API TYPE ARCH
+    if ! __parse_emu_img "${EMU_IMG}"; then
+        echo "\
+error: invalid emulator image name: ${EMU_IMG}
+  expected \"\${API}-\${TYPE}-\${ARCH}\" where API is a number, TYPE is one of
+  (def|goog|play), and ARCH is one of arm, arm64, x86, or x86_64." >&2
+        return 1
+    fi
+}
+
+docker_image_of_emu_img() {
+    echo "android-emulator-${1}"
+}
+
+# Check that the emulator image name has valid syntax and that the Docker image
+# is present. On failure, writes an error to stderr and exits the script.
+validate_emu_img() {
+    local EMU_IMG="${1}"
+    if ! validate_emu_img_syntax "${EMU_IMG}"; then
+        return 1
+    fi
+    # Make sure Docker is working before trusting other Docker commands.
+    # Temporarily suppress command echoing so we only show 'docker info' output
+    # on failure, and only once.
+    if (set +x; !(docker info &>/dev/null || docker info)); then
+        echo "error: Docker is required for emulator usage but 'docker info' failed" >&2
+        return 1
+    fi
+    local DOCKER_IMAGE=$(docker_image_of_emu_img ${EMU_IMG})
+    if ! docker image inspect ${DOCKER_IMAGE} &>/dev/null; then
+        echo "error: emulator Docker image (${DOCKER_IMAGE}) is not installed" >&2
+        return 1
+    fi
+}
+
+api_of_emu_img() {
+    local API TYPE ARCH
+    __parse_emu_img "${1}"
+    echo ${API}
+}
+
+type_of_emu_img() {
+    local API TYPE ARCH
+    __parse_emu_img "${1}"
+    echo ${TYPE}
+}
+
+arch_of_emu_img() {
+    local API TYPE ARCH
+    __parse_emu_img "${1}"
+    echo ${ARCH}
+}
+
+# Expand the short emu_img string into the full SDK package string identifying
+# the system image.
+sdk_package_of_emu_img() {
+    local API TYPE ARCH
+    __parse_emu_img "${1}"
+    echo "system-images;android-${API};${TYPE};$(abi_of_arch ${ARCH})"
+}
+
+# Return the Android ABI string for an architecture.
+abi_of_arch() {
+    case "${1}" in
+        arm) echo armeabi-v7a ;;
+        arm64) echo aarch64-v8a ;;
+        x86) echo x86 ;;
+        x86_64) echo x86_64 ;;
+        *) echo "error: unhandled arch ${1}" >&2; exit 1 ;;
+    esac
+}
+
+triple_of_arch() {
+    case "${1}" in
+        arm) echo armv7a-linux-androideabi ;;
+        arm64) echo aarch64-linux-android ;;
+        x86) echo i686-linux-android ;;
+        x86_64) echo x86_64-linux-android ;;
+        *) echo "error: unhandled arch ${1}" >&2; exit 1 ;;
+    esac
+}
diff --git a/libcxx/utils/ci/vendor/android/emulator-wait-for-ready.sh b/libcxx/utils/ci/vendor/android/emulator-wait-for-ready.sh
new file mode 100755
--- /dev/null
+++ b/libcxx/utils/ci/vendor/android/emulator-wait-for-ready.sh
@@ -0,0 +1,30 @@
+#!/usr/bin/env bash
+#===----------------------------------------------------------------------===##
+#
+# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+# See https://llvm.org/LICENSE.txt for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+#
+#===----------------------------------------------------------------------===##
+
+set -ex
+
+# Time to wait in seconds. The emulator ought to start in 5-15 seconds or so,
+# so add a safety factor in case something takes longer in CI.
+TIMEOUT=${1-300}
+
+# This syntax (using an IP address of 127.0.0.1 rather than localhost) seems to
+# prevent the adb client from ever spawning an adb host server.
+export ADB_SERVER_SOCKET=tcp:127.0.0.1:5037
+
+# Invoke nc first to ensure that something is listening to port 5037. Otherwise,
+# invoking adb might fork an adb server.
+#
+# TODO: Consider waiting for `adb shell getprop dev.bootcomplete 2>/dev/null
+# | grep 1 >/dev/null` as well. It adds ~4 seconds to 21-def-x86 and ~15 seconds
+# to 33-goog-x86_64 and doesn't seem to be necessary for running libc++ tests.
+timeout ${TIMEOUT} bash -c '
+until (nc -z localhost 5037 && adb wait-for-device); do
+    sleep 0.5
+done
+'
diff --git a/libcxx/utils/ci/vendor/android/setup-env-for-emulator.sh b/libcxx/utils/ci/vendor/android/setup-env-for-emulator.sh
new file mode 100644
--- /dev/null
+++ b/libcxx/utils/ci/vendor/android/setup-env-for-emulator.sh
@@ -0,0 +1,13 @@
+#===----------------------------------------------------------------------===##
+#
+# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+# See https://llvm.org/LICENSE.txt for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+#
+#===----------------------------------------------------------------------===##
+
+export ADB_SERVER_SOCKET="tcp:$(docker inspect \
+    -f '{{range.NetworkSettings.Networks}}{{.IPAddress}}{{end}}' \
+    libcxx-ci-android-emulator):5037"
+
+echo "setup-env-for-emulator.sh: setting ADB_SERVER_SOCKET to ${ADB_SERVER_SOCKET}"
diff --git a/libcxx/utils/ci/vendor/android/start-emulator.sh b/libcxx/utils/ci/vendor/android/start-emulator.sh
new file mode 100755
--- /dev/null
+++ b/libcxx/utils/ci/vendor/android/start-emulator.sh
@@ -0,0 +1,43 @@
+#!/usr/bin/env bash
+#===----------------------------------------------------------------------===##
+#
+# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+# See https://llvm.org/LICENSE.txt for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+#
+#===----------------------------------------------------------------------===##
+
+# Starts a new Docker container using a Docker image containing the Android
+# Emulator and an OS image. Stops and removes the old container if it exists
+# already.
+
+set -e
+
+THIS_DIR="$(cd "$(dirname "$0")" && pwd)"
+. "${THIS_DIR}/emulator-functions.sh"
+
+EMU_IMG="${1}"
+if ! validate_emu_img "${EMU_IMG}"; then
+    echo "error: The first argument must be a valid emulator image." >&2
+    exit 1
+fi
+
+"${THIS_DIR}/stop-emulator.sh"
+
+# Start the container.
+docker run --name libcxx-ci-android-emulator --detach --device /dev/kvm \
+    -eEMU_PARTITION_SIZE=8192 \
+    --volume android-platform-tools:/mnt/android-platform-tools \
+    $(docker_image_of_emu_img ${EMU_IMG})
+ERR=0
+docker exec libcxx-ci-android-emulator emulator-wait-for-ready.sh || ERR=${?}
+echo "Emulator container initial logs:"
+docker logs libcxx-ci-android-emulator
+if [ ${ERR} != 0 ]; then
+    exit ${ERR}
+fi
+
+# Make sure the device is accessible from outside the emulator container and
+# advertise to the user that this script exists.
+. "${THIS_DIR}/setup-env-for-emulator.sh"
+adb wait-for-device
diff --git a/libcxx/utils/ci/vendor/android/stop-emulator.sh b/libcxx/utils/ci/vendor/android/stop-emulator.sh
new file mode 100755
--- /dev/null
+++ b/libcxx/utils/ci/vendor/android/stop-emulator.sh
@@ -0,0 +1,25 @@
+#!/usr/bin/env bash
+#===----------------------------------------------------------------------===##
+#
+# 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
+#
+#===----------------------------------------------------------------------===##
+
+set -e
+
+THIS_DIR="$(cd "$(dirname "$0")" && pwd)"
+. "${THIS_DIR}/emulator-functions.sh"
+
+# Cleanup the emulator if it's already running.
+if docker container inspect libcxx-ci-android-emulator &>/dev/null; then
+    echo "Stopping existing emulator container..."
+    docker stop libcxx-ci-android-emulator
+
+    echo "Emulator container final logs:"
+    docker logs libcxx-ci-android-emulator
+
+    echo "Removing existing emulator container..."
+    docker rm libcxx-ci-android-emulator
+fi
diff --git a/libcxx/utils/libcxx/test/android.py b/libcxx/utils/libcxx/test/android.py
new file mode 100644
--- /dev/null
+++ b/libcxx/utils/libcxx/test/android.py
@@ -0,0 +1,97 @@
+#===----------------------------------------------------------------------===##
+#
+# 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
+#
+#===----------------------------------------------------------------------===##
+
+import atexit
+import os
+import re
+import select
+import socket
+import subprocess
+import tempfile
+import threading
+from typing import List
+
+
+def _get_cpu_count() -> int:
+    # Determine the number of cores by listing a /sys directory. Older devices
+    # lack `nproc`. Even if a static toybox binary is pushed to the device, it may
+    # return an incorrect value. (e.g. On a Nexus 7 running Android 5.0, toybox
+    # nproc returns 1 even though the device has 4 CPUs.)
+    job = subprocess.run(["adb", "shell", "ls /sys/devices/system/cpu"],
+                         encoding="utf8", check=False,
+                         stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+    if job.returncode == 1:
+        # Maybe adb is missing, maybe ANDROID_SERIAL needs to be defined, maybe the
+        # /sys subdir isn't there. Most errors will be handled later, just use one
+        # job. (N.B. The adb command still succeeds even if ls fails on older
+        # devices that lack the shell_v2 adb feature.)
+        return 1
+    # Make sure there are no CR characters in the output. Pre-shell_v2, the adb
+    # stdout comes from a master pty so newlines are CRLF-delimited. On Windows,
+    # LF might also get expanded to CRLF.
+    cpu_listing = job.stdout.replace('\r', '\n')
+
+    # Count lines that match "cpu${DIGITS}".
+    result = len([line for line in cpu_listing.splitlines()
+                  if re.match(r'cpu(\d)+$', line)])
+
+    # Restrict the result to something reasonable.
+    if result < 1:
+        result = 1
+    if result > 1024:
+        result = 1024
+
+    return result
+
+
+def _job_limit_socket_thread(temp_dir: tempfile.TemporaryDirectory,
+                             server: socket.socket, job_count: int) -> None:
+    """Service the job limit server socket, accepting only as many connections
+    as there should be concurrent jobs.
+    """
+    clients: List[socket.socket] = []
+    while True:
+        rlist = list(clients)
+        if len(clients) < job_count:
+            rlist.append(server)
+        rlist, _, _ = select.select(rlist, [], [])
+        for sock in rlist:
+            if sock == server:
+                new_client, _ = server.accept()
+                new_client.send(b"x")
+                clients.append(new_client)
+            else:
+                sock.close()
+                clients.remove(sock)
+
+
+def adb_job_limit_socket() -> str:
+    """An Android device can frequently have many fewer cores than the host
+    (e.g. 4 versus 128). We want to exploit all the device cores without
+    overburdening it.
+
+    Create a Unix domain socket that only allows as many connections as CPUs on
+    the Android device.
+    """
+
+    # Create the job limit server socket.
+    temp_dir = tempfile.TemporaryDirectory(prefix="libcxx_")
+    sock_addr = temp_dir.name + "/adb_job.sock"
+    server = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+    server.bind(sock_addr)
+    server.listen(1)
+
+    # Spawn a thread to service the socket. As a daemon thread, its existence
+    # won't prevent interpreter shutdown. The temp dir will still be removed on
+    # shutdown.
+    cpu_count = _get_cpu_count()
+    threading.Thread(target=_job_limit_socket_thread,
+                     args=(temp_dir, server, cpu_count),
+                     daemon=True).start()
+
+    return sock_addr
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
@@ -43,6 +43,17 @@
         return None
 
 
+def _getAndroidDeviceApi(cfg):
+    return int(programOutput(cfg, r"""
+        #include <android/api-level.h>
+        #include <stdio.h>
+        int main() {
+            printf("%d\n", android_get_device_api_level());
+            return 0;
+        }
+    """))
+
+
 DEFAULT_FEATURES = [
     Feature(
         name="thread-safety",
@@ -387,6 +398,15 @@
         actions=[AddCompileFlag("-DTEST_WINDOWS_DLL")],
     ),
     Feature(name="linux", when=lambda cfg: "__linux__" in compilerMacros(cfg)),
+    Feature(name="android", when=lambda cfg: "__ANDROID__" in compilerMacros(cfg)),
+    Feature(
+        name=lambda cfg: "android-device-api={}".format(_getAndroidDeviceApi(cfg)),
+        when=lambda cfg: "__ANDROID__" in compilerMacros(cfg),
+    ),
+    Feature(
+        name="LIBCXX-ANDROID-FIXME",
+        when=lambda cfg: "__ANDROID__" in compilerMacros(cfg),
+    ),
     Feature(name="netbsd", when=lambda cfg: "__NetBSD__" in compilerMacros(cfg)),
     Feature(name="freebsd", when=lambda cfg: "__FreeBSD__" in compilerMacros(cfg)),
     Feature(
diff --git a/libcxxabi/test/configs/llvm-libc++abi-android-ndk.cfg.in b/libcxxabi/test/configs/llvm-libc++abi-android-ndk.cfg.in
new file mode 100644
--- /dev/null
+++ b/libcxxabi/test/configs/llvm-libc++abi-android-ndk.cfg.in
@@ -0,0 +1,40 @@
+# This testing configuration handles running the test suite against LLVM's
+# libc++abi using adb and a libc++_shared.so library on Android.
+
+lit_config.load_config(config, '@CMAKE_CURRENT_BINARY_DIR@/cmake-bridge.cfg')
+
+import re
+import site
+
+site.addsitedir(os.path.join('@LIBCXX_SOURCE_DIR@', 'utils'))
+
+import libcxx.test.android
+import libcxx.test.config
+import libcxx.test.params
+
+config.substitutions.append(('%{flags}',
+    '--sysroot @CMAKE_SYSROOT@' if '@CMAKE_SYSROOT@' else ''
+))
+config.substitutions.append(('%{compile_flags}',
+    '-nostdinc++ -I %{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'
+))
+
+# The NDK library is called "libc++_shared.so". Use LD_LIBRARY_PATH to find
+# libc++_shared.so because older Bionic dynamic loaders don't support rpath
+# lookup. The Android libc++ shared library exports libc++abi, so we don't need
+# to link with -lc++abi.
+config.substitutions.append(('%{link_flags}',
+    '-nostdlib++ -L %{lib} -lc++_shared'
+))
+config.substitutions.append(('%{exec}',
+    '%{executor}' +
+    ' --job-limit-socket ' + libcxx.test.android.adb_job_limit_socket() +
+    ' --prepend-path-env LD_LIBRARY_PATH /data/local/tmp/libc++ --execdir %T -- '
+))
+
+libcxx.test.config.configure(
+    libcxx.test.params.DEFAULT_PARAMETERS,
+    libcxx.test.features.DEFAULT_FEATURES,
+    config,
+    lit_config
+)
diff --git a/libcxxabi/test/test_demangle.pass.cpp b/libcxxabi/test/test_demangle.pass.cpp
--- a/libcxxabi/test/test_demangle.pass.cpp
+++ b/libcxxabi/test/test_demangle.pass.cpp
@@ -14,6 +14,10 @@
 // UNSUPPORTED: stdlib=apple-libc++ && target={{.+}}-apple-macosx10.{{9|10|11|12|13|14|15}}
 // UNSUPPORTED: stdlib=apple-libc++ && target={{.+}}-apple-macosx11.0
 
+// Android's long double on x86[-64] is (64/128)-bits instead of Linux's usual
+// 80-bit format, and this demangling test is failing on it.
+// XFAIL: LIBCXX-ANDROID-FIXME && target={{i686|x86_64}}-{{.+}}-android{{.*}}
+
 #include "support/timer.h"
 #include <algorithm>
 #include <cassert>
diff --git a/llvm/utils/lit/lit/TestingConfig.py b/llvm/utils/lit/lit/TestingConfig.py
--- a/llvm/utils/lit/lit/TestingConfig.py
+++ b/llvm/utils/lit/lit/TestingConfig.py
@@ -43,6 +43,7 @@
             "TSAN_OPTIONS",
             "UBSAN_OPTIONS",
             "ADB",
+            "ADB_SERVER_SOCKET",
             "ANDROID_SERIAL",
             "SSH_AUTH_SOCK",
             "SANITIZER_IGNORE_CVE_2016_2143",
diff --git a/runtimes/cmake/android/Arch-arm.cmake b/runtimes/cmake/android/Arch-arm.cmake
new file mode 100644
--- /dev/null
+++ b/runtimes/cmake/android/Arch-arm.cmake
@@ -0,0 +1,7 @@
+include(${CMAKE_CURRENT_LIST_DIR}/Common.cmake)
+
+set(CMAKE_SYSTEM_PROCESSOR "armv7-a" CACHE STRING "")
+set(CMAKE_ASM_COMPILER_TARGET "armv7a-linux-androideabi21" CACHE STRING "")
+set(CMAKE_C_COMPILER_TARGET   "armv7a-linux-androideabi21" CACHE STRING "")
+set(CMAKE_CXX_COMPILER_TARGET "armv7a-linux-androideabi21" CACHE STRING "")
+set(ANDROID_NATIVE_API_LEVEL 21 CACHE STRING "")
diff --git a/runtimes/cmake/android/Arch-arm64.cmake b/runtimes/cmake/android/Arch-arm64.cmake
new file mode 100644
--- /dev/null
+++ b/runtimes/cmake/android/Arch-arm64.cmake
@@ -0,0 +1,7 @@
+include(${CMAKE_CURRENT_LIST_DIR}/Common.cmake)
+
+set(CMAKE_SYSTEM_PROCESSOR "aarch64" CACHE STRING "")
+set(CMAKE_ASM_COMPILER_TARGET "aarch64-linux-android21" CACHE STRING "")
+set(CMAKE_C_COMPILER_TARGET   "aarch64-linux-android21" CACHE STRING "")
+set(CMAKE_CXX_COMPILER_TARGET "aarch64-linux-android21" CACHE STRING "")
+set(ANDROID_NATIVE_API_LEVEL 21 CACHE STRING "")
diff --git a/runtimes/cmake/android/Arch-x86.cmake b/runtimes/cmake/android/Arch-x86.cmake
new file mode 100644
--- /dev/null
+++ b/runtimes/cmake/android/Arch-x86.cmake
@@ -0,0 +1,7 @@
+include(${CMAKE_CURRENT_LIST_DIR}/Common.cmake)
+
+set(CMAKE_SYSTEM_PROCESSOR "i686" CACHE STRING "")
+set(CMAKE_ASM_COMPILER_TARGET "i686-linux-android21" CACHE STRING "")
+set(CMAKE_C_COMPILER_TARGET   "i686-linux-android21" CACHE STRING "")
+set(CMAKE_CXX_COMPILER_TARGET "i686-linux-android21" CACHE STRING "")
+set(ANDROID_NATIVE_API_LEVEL 21 CACHE STRING "")
diff --git a/runtimes/cmake/android/Arch-x86_64.cmake b/runtimes/cmake/android/Arch-x86_64.cmake
new file mode 100644
--- /dev/null
+++ b/runtimes/cmake/android/Arch-x86_64.cmake
@@ -0,0 +1,7 @@
+include(${CMAKE_CURRENT_LIST_DIR}/Common.cmake)
+
+set(CMAKE_SYSTEM_PROCESSOR "x86_64" CACHE STRING "")
+set(CMAKE_ASM_COMPILER_TARGET "x86_64-linux-android21" CACHE STRING "")
+set(CMAKE_C_COMPILER_TARGET   "x86_64-linux-android21" CACHE STRING "")
+set(CMAKE_CXX_COMPILER_TARGET "x86_64-linux-android21" CACHE STRING "")
+set(ANDROID_NATIVE_API_LEVEL 21 CACHE STRING "")
diff --git a/runtimes/cmake/android/Common.cmake b/runtimes/cmake/android/Common.cmake
new file mode 100644
--- /dev/null
+++ b/runtimes/cmake/android/Common.cmake
@@ -0,0 +1,6 @@
+set(CMAKE_SYSTEM_NAME "Android" CACHE STRING "")
+
+# Set the CMake system version to "1" to inhibit CMake's built-in support for
+# compiling using the Android NDK, which gets in the way when we're not using an
+# NDK.
+set(CMAKE_SYSTEM_VERSION "1" CACHE STRING "")