diff --git a/libcxx/test/std/input.output/filesystems/class.path/path.member/path.charconv.pass.cpp b/libcxx/test/std/input.output/filesystems/class.path/path.member/path.charconv.pass.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/std/input.output/filesystems/class.path/path.member/path.charconv.pass.cpp
@@ -0,0 +1,418 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03
+// ADDITIONAL_COMPILE_FLAGS: -D_LIBCPP_DISABLE_DEPRECATION_WARNINGS
+
+// <filesystem>
+
+// class path
+
+// Test constructors, accessors and modifiers that convert from/to various
+// character encodings. Constructors and modifiers (append, concat,
+// operator/=, operator+=) accept inputs with various character encodings,
+// and accessors (*string(), string<>(), u8string()) export the string with
+// various encodings.
+//
+// Some encodings are standardized; char16_t, char32_t and the u8string
+// accessor and u8path constructor (and normal functions taking char8_t in
+// C++20) convert from/to UTF-16, UTF-32 and UTF-8. wchar_t can be either
+// UTF-16 or UTF-32 depending on the size of the wchar_t type, or can be
+// left unimplemented.
+//
+// Plain char is implicitly UTF-8 on posix systems. On Windows, plain char
+// is supposed to be in the same encoding as the platform's native file
+// system APIs consumes in the functions that take narrow strings as path
+// names.
+
+
+#include "filesystem_include.h"
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "filesystem_test_helper.h"
+
+// libstdc++ doesn't define conversions from/to wchar_t outside of windows.
+#if defined(__GLIBCXX__) && !defined(_WIN32)
+#  define HAS_NO_WCHAR
+#endif
+
+// Test conversion with strings that fit within the latin1 charset, that fit
+// within one code point in UTF-16, and that can be expressible in certain
+// one-byte code pages.
+static void test_latin_unicode()
+{
+  const char16_t u16str[] = { 0xe5, 0xe4, 0xf6, 0x00 };
+  const char32_t u32str[] = { 0xe5, 0xe4, 0xf6, 0x00 };
+  const char str[] = { char(0xc3), char(0xa5), char(0xc3), char(0xa4), char(0xc3), char(0xb6), 0x00 }; // UTF8, in a regular char string
+#if TEST_STD_VER > 17 && defined(__cpp_lib_char8_t)
+  const char8_t u8str[] = { 0xc3, 0xa5, 0xc3, 0xa4, 0xc3, 0xb6, 0x00 };
+#else
+  const char u8str[] = { char(0xc3), char(0xa5), char(0xc3), char(0xa4), char(0xc3), char(0xb6), 0x00 };
+#endif
+#ifndef HAS_NO_WCHAR
+  const wchar_t wstr[] = { 0xe5, 0xe4, 0xf6, 0x00 };
+#endif
+
+  // Test well-defined conversion between UTF-8, UTF-16 and UTF-32
+  {
+    const fs::path p(u16str);
+    assert(p.u8string() == u8str);
+    assert(p.u16string() == u16str);
+    assert(p.u32string() == u32str);
+    assert(p.string<char16_t>() == u16str);
+    assert(p.string<char32_t>() == u32str);
+  }
+  {
+    const fs::path p(u32str);
+    assert(p.u8string() == u8str);
+    assert(p.u16string() == u16str);
+    assert(p.u32string() == u32str);
+    assert(p.string<char16_t>() == u16str);
+    assert(p.string<char32_t>() == u32str);
+  }
+  {
+    const fs::path p = fs::u8path(str);
+    assert(p.u8string() == u8str);
+    assert(p.u16string() == u16str);
+    assert(p.u32string() == u32str);
+    assert(p.string<char16_t>() == u16str);
+    assert(p.string<char32_t>() == u32str);
+  }
+#if TEST_STD_VER > 17 && defined(__cpp_lib_char8_t)
+  {
+    // In C++20, the path constructor can unambiguously handle UTF-8 input,
+    // even if the plain char constructor would treat it as something else.
+    const fs::path p(u8str);
+    assert(p.u8string() == u8str);
+    assert(p.u16string() == u16str);
+    assert(p.u32string() == u32str);
+    assert(p.string<char8_t>() == u8str);
+    assert(p.string<char16_t>() == u16str);
+    assert(p.string<char32_t>() == u32str);
+  }
+  // Check reading various inputs with string<char8_t>()
+  {
+    const fs::path p(u16str);
+    assert(p.string<char8_t>() == u8str);
+  }
+  {
+    const fs::path p(u32str);
+    assert(p.string<char8_t>() == u8str);
+  }
+  {
+    const fs::path p = fs::u8path(str);
+    assert(p.string<char8_t>() == u8str);
+  }
+#endif
+#ifndef HAS_NO_WCHAR
+  // Test conversion to/from wchar_t.
+  {
+    const fs::path p(u16str);
+    assert(p.wstring() == wstr);
+    assert(p.string<wchar_t>() == wstr);
+  }
+  {
+    const fs::path p = fs::u8path(str);
+    assert(p.wstring() == wstr);
+    assert(p.string<wchar_t>() == wstr);
+  }
+  {
+    const fs::path p(wstr);
+    assert(p.wstring() == wstr);
+    assert(p.u8string() == u8str);
+    assert(p.u16string() == u16str);
+    assert(p.u32string() == u32str);
+    assert(p.string<wchar_t>() == wstr);
+  }
+#endif
+#ifndef _WIN32
+  // Test conversion to/from regular char-based string. On POSIX, this
+  // is implied to convert to/from UTF-8.
+  {
+    const fs::path p(str);
+    assert(p.string() == str);
+    assert(p.u16string() == u16str);
+    assert(p.string<char>() == str);
+  }
+  {
+    const fs::path p(u16str);
+    assert(p.string() == str);
+    assert(p.string<char>() == str);
+  }
+#else
+  // On windows, the narrow char-based input/output is supposed to be
+  // in the charset that narrow file IO APIs use. This can either be the
+  // current active code page (ACP) or the OEM code page, exposed by
+  // the AreFileApisANSI() function, and settable with SetFileApisToANSI() and
+  // SetFileApisToOEM(). We can't set which codepage is active within
+  // the process, but for some specific known ones, we can check if they
+  // behave as expected.
+  SetFileApisToANSI();
+  if (GetACP() == 1252) {
+    const char latin1[] = { char(0xe5), char(0xe4), char(0xf6), 0x00 };
+    {
+      const fs::path p(wstr);
+      assert(p.string() == latin1);
+      assert(p.string<char>() == latin1);
+    }
+    {
+      const fs::path p(latin1);
+      assert(p.string() == latin1);
+      assert(p.wstring() == wstr);
+      assert(p.u8string() == u8str);
+      assert(p.u16string() == u16str);
+      assert(p.string<char>() == latin1);
+      assert(p.string<wchar_t>() == wstr);
+    }
+  }
+  SetFileApisToOEM();
+  if (GetOEMCP() == 850 || GetOEMCP() == 437) {
+    // These chars are identical in both CP 850 and 437
+    const char cp850[] = { char(0x86), char(0x84), char(0x94), 0x00 };
+    {
+      const fs::path p(wstr);
+      assert(p.string() == cp850);
+      assert(p.string<char>() == cp850);
+    }
+    {
+      const fs::path p(cp850);
+      assert(p.string() == cp850);
+      assert(p.wstring() == wstr);
+      assert(p.u8string() == u8str);
+      assert(p.u16string() == u16str);
+      assert(p.string<char>() == cp850);
+      assert(p.string<wchar_t>() == wstr);
+    }
+  }
+#endif
+}
+
+// Test conversion with strings that don't fit within one UTF-16 code point.
+// Here, wchar_t can be either UTF-16 or UTF-32 depending on the size on the
+// particular platform.
+static void test_wide_unicode()
+{
+  const char16_t u16str[] = { 0xd801, 0xdc37, 0x00 };
+  const char32_t u32str[] = { 0x10437, 0x00 };
+#if TEST_STD_VER > 17 && defined(__cpp_lib_char8_t)
+  const char8_t u8str[] = { 0xf0, 0x90, 0x90, 0xb7, 0x00 };
+#else
+  const char u8str[] = { char(0xf0), char(0x90), char(0x90), char(0xb7), 0x00 };
+#endif
+  const char str[] = { char(0xf0), char(0x90), char(0x90), char(0xb7), 0x00 };
+  {
+    const fs::path p = fs::u8path(str);
+    assert(p.u8string() == u8str);
+    assert(p.u16string() == u16str);
+    assert(p.u32string() == u32str);
+  }
+  {
+    const fs::path p(u16str);
+    assert(p.u8string() == u8str);
+    assert(p.u16string() == u16str);
+    assert(p.u32string() == u32str);
+  }
+  {
+    const fs::path p(u32str);
+    assert(p.u8string() == u8str);
+    assert(p.u16string() == u16str);
+    assert(p.u32string() == u32str);
+  }
+#if !defined(HAS_NO_WCHAR) && defined(__SIZEOF_WCHAR_T__)
+#if __SIZEOF_WCHAR_T__ == 2
+  const wchar_t wstr[] = { 0xd801, 0xdc37, 0x00 };
+#else
+  const wchar_t wstr[] = { 0x10437, 0x00 };
+#endif
+  // Test conversion to/from wchar_t.
+  // libstdc++ doesn't define conversions from/to wchar_t outside of windows.
+  {
+    const fs::path p = fs::u8path(str);
+    assert(p.wstring() == wstr);
+  }
+  {
+    const fs::path p(u16str);
+    assert(p.wstring() == wstr);
+  }
+  {
+    const fs::path p(u32str);
+    assert(p.wstring() == wstr);
+  }
+  {
+    const fs::path p(wstr);
+    assert(p.u8string() == u8str);
+    assert(p.u16string() == u16str);
+    assert(p.u32string() == u32str);
+    assert(p.wstring() == wstr);
+  }
+#endif
+}
+
+// Test appending paths in different encodings.
+static void test_append()
+{
+  const char16_t u16str[] = { 0xd801, 0xdc37, 0x00 };
+  const char32_t u32str[] = { 0x10437, 0x00 };
+  const char32_t u32ref[] = { 0x10437, fs::path::preferred_separator, 0x10437, fs::path::preferred_separator, 0x10437, 0x00 };
+  const char str[] = { char(0xf0), char(0x90), char(0x90), char(0xb7), 0x00 };
+  {
+    fs::path p = fs::u8path(str) / u16str / u32str;
+    assert(p.u32string() == u32ref);
+    p = fs::u8path(str).append(u16str).append(u32str);
+    assert(p.u32string() == u32ref);
+    p = fs::u8path(str);
+    p /= u16str;
+    p /= u32str;
+    assert(p.u32string() == u32ref);
+  }
+#if !defined(HAS_NO_WCHAR) && defined(__SIZEOF_WCHAR_T__)
+#if __SIZEOF_WCHAR_T__ == 2
+  const wchar_t wstr[] = { 0xd801, 0xdc37, 0x00 };
+#else
+  const wchar_t wstr[] = { 0x10437, 0x00 };
+#endif
+  // Test conversion from wchar_t.
+  // libstdc++ doesn't define conversions from/to wchar_t outside of windows.
+  {
+    fs::path p = fs::path(u16str) / wstr / u32str;
+    assert(p.u32string() == u32ref);
+    p = fs::path(u16str).append(wstr).append(u32str);
+    assert(p.u32string() == u32ref);
+    p = fs::path(u16str);
+    p /= wstr;
+    p /= u32str;
+    assert(p.u32string() == u32ref);
+  }
+#endif
+}
+
+static void test_concat()
+{
+  const char16_t u16str[] = { 0xd801, 0xdc37, 0x00 };
+  const char32_t u32str[] = { 0x10437, 0x00 };
+  const char32_t u32ref[] = { 0x10437, 0x10437, 0x10437, 0x00 };
+  const char str[] = { char(0xf0), char(0x90), char(0x90), char(0xb7), 0x00 };
+  {
+    fs::path p = fs::u8path(str);
+    p += u16str;
+    p += u32str;
+    assert(p.u32string() == u32ref);
+    p = fs::u8path(str).concat(u16str).concat(u32str);
+    assert(p.u32string() == u32ref);
+  }
+#if !defined(HAS_NO_WCHAR) && defined(__SIZEOF_WCHAR_T__)
+#if __SIZEOF_WCHAR_T__ == 2
+  const wchar_t wstr[] = { 0xd801, 0xdc37, 0x00 };
+#else
+  const wchar_t wstr[] = { 0x10437, 0x00 };
+#endif
+  // Test conversion from wchar_t.
+  // libstdc++ doesn't define conversions from/to wchar_t outside of windows.
+  {
+    fs::path p = fs::path(u16str);
+    p += wstr;
+    p += u32str;
+    assert(p.u32string() == u32ref);
+    p = fs::path(u16str).concat(wstr).concat(u32str);
+    assert(p.u32string() == u32ref);
+  }
+#endif
+}
+
+static void test_append_concat_narrow()
+{
+  const char16_t u16str[] = { 0xe5, 0x00 };
+  const char32_t u32ref_append[] = { 0xe5, fs::path::preferred_separator, 0xe5, 0x00 };
+  const char32_t u32ref_concat[] = { 0xe5, 0xe5, 0x00 };
+
+#if TEST_STD_VER > 17 && defined(__cpp_lib_char8_t)
+  {
+    const char8_t u8str[] = { 0xc3, 0xa5, 0x00 };
+    // In C++20, appends of a char8_t string is unambiguously treated as
+    // UTF-8.
+    fs::path p = fs::path(u16str) / u8str;
+    assert(p.u32string() == u32ref_append);
+    p = fs::path(u16str).append(u8str);
+    assert(p.u32string() == u32ref_append);
+    p = fs::path(u16str);
+    p /= u8str;
+    assert(p.u32string() == u32ref_append);
+    p = fs::path(u16str).concat(u8str);
+    assert(p.u32string() == u32ref_concat);
+    p = fs::path(u16str);
+    p += u8str;
+    assert(p.u32string() == u32ref_concat);
+  }
+#endif
+#ifndef _WIN32
+  // Test appending a regular char-based string. On POSIX, this
+  // is implied to convert to/from UTF-8.
+  {
+    const char str[] = { char(0xc3), char(0xa5), 0x00 }; // UTF8, in a regular char string
+    fs::path p = fs::path(u16str) / str;
+    assert(p.u32string() == u32ref_append);
+    p = fs::path(u16str).append(str);
+    assert(p.u32string() == u32ref_append);
+    p = fs::path(u16str);
+    p /= str;
+    assert(p.u32string() == u32ref_append);
+    p = fs::path(u16str).concat(str);
+    assert(p.u32string() == u32ref_concat);
+    p = fs::path(u16str);
+    p += str;
+    assert(p.u32string() == u32ref_concat);
+  }
+#else
+  SetFileApisToANSI();
+  if (GetACP() == 1252) {
+    const char latin1[] = { char(0xe5), 0x00 };
+    fs::path p = fs::path(u16str) / latin1;
+    assert(p.u32string() == u32ref_append);
+    p = fs::path(u16str).append(latin1);
+    assert(p.u32string() == u32ref_append);
+    p = fs::path(u16str);
+    p /= latin1;
+    assert(p.u32string() == u32ref_append);
+    p = fs::path(u16str).concat(latin1);
+    assert(p.u32string() == u32ref_concat);
+    p = fs::path(u16str);
+    p += latin1;
+    assert(p.u32string() == u32ref_concat);
+  }
+  SetFileApisToOEM();
+  if (GetOEMCP() == 850 || GetOEMCP() == 437) {
+    // This chars is identical in both CP 850 and 437
+    const char cp850[] = { char(0x86), 0x00 };
+    fs::path p = fs::path(u16str) / cp850;
+    assert(p.u32string() == u32ref_append);
+    p = fs::path(u16str).append(cp850);
+    assert(p.u32string() == u32ref_append);
+    p = fs::path(u16str);
+    p /= cp850;
+    assert(p.u32string() == u32ref_append);
+    p = fs::path(u16str).concat(cp850);
+    assert(p.u32string() == u32ref_concat);
+    p = fs::path(u16str);
+    p += cp850;
+    assert(p.u32string() == u32ref_concat);
+  }
+#endif
+}
+
+int main(int, char**)
+{
+  test_latin_unicode();
+  test_wide_unicode();
+  test_append();
+  test_concat();
+  test_append_concat_narrow();
+
+  return 0;
+}