diff --git a/lib/libcxx/include/__config b/lib/libcxx/include/__config
index af241b40958682d8aa5dfbd50a89dc418014dbbf..b94483274c24ee0ac222518ddc677c79bd660bfd 100644
--- a/lib/libcxx/include/__config
+++ b/lib/libcxx/include/__config
@@ -235,7 +235,9 @@ typedef __char32_t char32_t;
         defined(__APPLE__) ||                                                                                          \
         defined(__MVS__) ||                                                                                            \
         defined(_AIX) ||                                                                                               \
-        defined(__EMSCRIPTEN__)
+        defined(__EMSCRIPTEN__) ||                                                                                     \
+        defined(__HAIKU__)
+// zig patch: haiku support
 // clang-format on
 #      undef _LIBCPP_HAS_THREAD_API_PTHREAD
 #      define _LIBCPP_HAS_THREAD_API_PTHREAD 1
diff --git a/lib/libcxx/include/__locale b/lib/libcxx/include/__locale
index bb8f8e7bbf5d9cc82d9d45fd539ee1760da33482..be6beb4582fa3a878ba6122d69ba5c1d1ba5c17c 100644
--- a/lib/libcxx/include/__locale
+++ b/lib/libcxx/include/__locale
@@ -454,6 +454,20 @@ public:
   static const mask blank  = __ISBLANK;
 #    endif
   static const mask __regex_word = 0x8000;
+// zig patch: haiku support
+#  elif defined(__HAIKU__)
+  typedef unsigned short mask;
+  static const mask space        = _ISspace;
+  static const mask print        = _ISprint;
+  static const mask cntrl        = _IScntrl;
+  static const mask upper        = _ISupper;
+  static const mask lower        = _ISlower;
+  static const mask alpha        = _ISalpha;
+  static const mask digit        = _ISdigit;
+  static const mask punct        = _ISpunct;
+  static const mask xdigit       = _ISxdigit;
+  static const mask blank        = _ISblank;
+  static const mask __regex_word = 0x80;
 #  else
 #    error unknown rune table for this platform -- do you mean to define _LIBCPP_PROVIDES_DEFAULT_RUNE_TABLE?
 #  endif
diff --git a/lib/libcxx/include/__locale_dir/locale_base_api.h b/lib/libcxx/include/__locale_dir/locale_base_api.h
index f973d95ef244d58dafc774d6ceb9a68ceeb08300..2e315625cfb621f6c6bbb7788213f2b7058826a2 100644
--- a/lib/libcxx/include/__locale_dir/locale_base_api.h
+++ b/lib/libcxx/include/__locale_dir/locale_base_api.h
@@ -128,6 +128,9 @@
 #    include <__locale_dir/support/newlib.h>
 #  elif defined(_AIX)
 #    include <__locale_dir/support/aix.h>
+// zig patch: haiku support
+#  elif defined(__HAIKU__)
+#    include <__locale_dir/support/haiku.h>
 #  else
 
 // TODO: This is a temporary definition to bridge between the old way we defined the locale base API
diff --git a/lib/libcxx/include/__locale_dir/support/haiku.h b/lib/libcxx/include/__locale_dir/support/haiku.h
new file mode 100644
index 0000000000000000000000000000000000000000..0e33350c6a5522ae09e277d440b8e78e77c4f955
--- /dev/null
+++ b/lib/libcxx/include/__locale_dir/support/haiku.h
@@ -0,0 +1,243 @@
+// zig patch: haiku support
+//===-----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___LOCALE_DIR_SUPPORT_HAIKU_H
+#define _LIBCPP___LOCALE_DIR_SUPPORT_HAIKU_H
+
+#include <__config>
+#include <cctype>
+#include <clocale>
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#if _LIBCPP_HAS_WIDE_CHARACTERS
+#  include <cwchar>
+#  include <cwctype>
+#endif
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+namespace __locale {
+
+struct __locale_guard {
+  _LIBCPP_HIDE_FROM_ABI __locale_guard(locale_t& __loc) : __old_loc_(::uselocale(__loc)) {}
+
+  _LIBCPP_HIDE_FROM_ABI ~__locale_guard() {
+    if (__old_loc_)
+      ::uselocale(__old_loc_);
+  }
+
+  locale_t __old_loc_;
+
+  __locale_guard(__locale_guard const&)            = delete;
+  __locale_guard& operator=(__locale_guard const&) = delete;
+};
+
+//
+// Locale management
+//
+#define _LIBCPP_COLLATE_MASK LC_COLLATE_MASK
+#define _LIBCPP_CTYPE_MASK LC_CTYPE_MASK
+#define _LIBCPP_MONETARY_MASK LC_MONETARY_MASK
+#define _LIBCPP_NUMERIC_MASK LC_NUMERIC_MASK
+#define _LIBCPP_TIME_MASK LC_TIME_MASK
+#define _LIBCPP_MESSAGES_MASK LC_MESSAGES_MASK
+#define _LIBCPP_ALL_MASK LC_ALL_MASK
+#define _LIBCPP_LC_ALL LC_ALL
+
+using __locale_t _LIBCPP_NODEBUG = ::locale_t;
+
+#if defined(_LIBCPP_BUILDING_LIBRARY)
+using __lconv_t _LIBCPP_NODEBUG = std::lconv;
+
+inline _LIBCPP_HIDE_FROM_ABI __locale_t __newlocale(int __category_mask, const char* __locale, __locale_t __base) {
+  return ::newlocale(__category_mask, __locale, __base);
+}
+
+inline _LIBCPP_HIDE_FROM_ABI void __freelocale(__locale_t __loc) { ::freelocale(__loc); }
+
+inline _LIBCPP_HIDE_FROM_ABI char* __setlocale(int __category, char const* __locale) {
+  return ::setlocale(__category, __locale);
+}
+
+inline _LIBCPP_HIDE_FROM_ABI __lconv_t* __localeconv(__locale_t& __loc) {
+  __locale_guard __current(__loc);
+  return std::localeconv();
+}
+#endif // _LIBCPP_BUILDING_LIBRARY
+
+//
+// Strtonum functions
+//
+inline _LIBCPP_HIDE_FROM_ABI float __strtof(const char* __nptr, char** __endptr, __locale_t __loc) {
+  __locale_guard __current(__loc);
+  return std::strtof(__nptr, __endptr);
+}
+
+inline _LIBCPP_HIDE_FROM_ABI double __strtod(const char* __nptr, char** __endptr, __locale_t __loc) {
+  __locale_guard __current(__loc);
+  return std::strtod(__nptr, __endptr);
+}
+
+inline _LIBCPP_HIDE_FROM_ABI long double __strtold(const char* __nptr, char** __endptr, __locale_t __loc) {
+  __locale_guard __current(__loc);
+  return std::strtold(__nptr, __endptr);
+}
+
+//
+// Character manipulation functions
+//
+#if defined(_LIBCPP_BUILDING_LIBRARY)
+inline _LIBCPP_HIDE_FROM_ABI int __toupper(int __c, __locale_t __loc) { return ::toupper_l(__c, __loc); }
+
+inline _LIBCPP_HIDE_FROM_ABI int __tolower(int __c, __locale_t __loc) { return ::tolower_l(__c, __loc); }
+
+inline _LIBCPP_HIDE_FROM_ABI int __strcoll(const char* __s1, const char* __s2, __locale_t __loc) {
+  return ::strcoll_l(__s1, __s2, __loc);
+}
+
+inline _LIBCPP_HIDE_FROM_ABI size_t __strxfrm(char* __dest, const char* __src, size_t __n, __locale_t __loc) {
+  return ::strxfrm_l(__dest, __src, __n, __loc);
+}
+
+#  if _LIBCPP_HAS_WIDE_CHARACTERS
+inline _LIBCPP_HIDE_FROM_ABI int __iswctype(wint_t __c, wctype_t __type, __locale_t __loc) {
+  return ::iswctype_l(__c, __type, __loc);
+}
+
+inline _LIBCPP_HIDE_FROM_ABI int __iswspace(wint_t __c, __locale_t __loc) { return ::iswspace_l(__c, __loc); }
+
+inline _LIBCPP_HIDE_FROM_ABI int __iswprint(wint_t __c, __locale_t __loc) { return ::iswprint_l(__c, __loc); }
+
+inline _LIBCPP_HIDE_FROM_ABI int __iswcntrl(wint_t __c, __locale_t __loc) { return ::iswcntrl_l(__c, __loc); }
+
+inline _LIBCPP_HIDE_FROM_ABI int __iswupper(wint_t __c, __locale_t __loc) { return ::iswupper_l(__c, __loc); }
+
+inline _LIBCPP_HIDE_FROM_ABI int __iswlower(wint_t __c, __locale_t __loc) { return ::iswlower_l(__c, __loc); }
+
+inline _LIBCPP_HIDE_FROM_ABI int __iswalpha(wint_t __c, __locale_t __loc) { return ::iswalpha_l(__c, __loc); }
+
+inline _LIBCPP_HIDE_FROM_ABI int __iswblank(wint_t __c, __locale_t __loc) { return ::iswblank_l(__c, __loc); }
+
+inline _LIBCPP_HIDE_FROM_ABI int __iswdigit(wint_t __c, __locale_t __loc) { return ::iswdigit_l(__c, __loc); }
+
+inline _LIBCPP_HIDE_FROM_ABI int __iswpunct(wint_t __c, __locale_t __loc) { return ::iswpunct_l(__c, __loc); }
+
+inline _LIBCPP_HIDE_FROM_ABI int __iswxdigit(wint_t __c, __locale_t __loc) { return ::iswxdigit_l(__c, __loc); }
+
+inline _LIBCPP_HIDE_FROM_ABI wint_t __towupper(wint_t __c, __locale_t __loc) { return ::towupper_l(__c, __loc); }
+
+inline _LIBCPP_HIDE_FROM_ABI wint_t __towlower(wint_t __c, __locale_t __loc) { return ::towlower_l(__c, __loc); }
+
+inline _LIBCPP_HIDE_FROM_ABI int __wcscoll(const wchar_t* __ws1, const wchar_t* __ws2, __locale_t __loc) {
+  return ::wcscoll_l(__ws1, __ws2, __loc);
+}
+
+inline _LIBCPP_HIDE_FROM_ABI size_t __wcsxfrm(wchar_t* __dest, const wchar_t* __src, size_t __n, __locale_t __loc) {
+  return ::wcsxfrm_l(__dest, __src, __n, __loc);
+}
+#  endif // _LIBCPP_HAS_WIDE_CHARACTERS
+
+inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_ATTRIBUTE_FORMAT(__strftime__, 3, 0) size_t
+    __strftime(char* __s, size_t __max, const char* __format, const struct tm* __tm, __locale_t __loc) {
+  return ::strftime_l(__s, __max, __format, __tm, __loc);
+}
+
+//
+// Other functions
+//
+inline _LIBCPP_HIDE_FROM_ABI decltype(MB_CUR_MAX) __mb_len_max(__locale_t __loc) {
+  __locale_guard __current(__loc);
+  return MB_CUR_MAX;
+}
+
+#  if _LIBCPP_HAS_WIDE_CHARACTERS
+inline _LIBCPP_HIDE_FROM_ABI wint_t __btowc(int __c, __locale_t __loc) {
+  __locale_guard __current(__loc);
+  return std::btowc(__c);
+}
+
+inline _LIBCPP_HIDE_FROM_ABI int __wctob(wint_t __c, __locale_t __loc) {
+  __locale_guard __current(__loc);
+  return std::wctob(__c);
+}
+
+inline _LIBCPP_HIDE_FROM_ABI size_t
+__wcsnrtombs(char* __dest, const wchar_t** __src, size_t __nwc, size_t __len, mbstate_t* __ps, __locale_t __loc) {
+  __locale_guard __current(__loc);
+  return ::wcsnrtombs(__dest, __src, __nwc, __len, __ps); // non-standard
+}
+
+inline _LIBCPP_HIDE_FROM_ABI size_t __wcrtomb(char* __s, wchar_t __wc, mbstate_t* __ps, __locale_t __loc) {
+  __locale_guard __current(__loc);
+  return std::wcrtomb(__s, __wc, __ps);
+}
+
+inline _LIBCPP_HIDE_FROM_ABI size_t
+__mbsnrtowcs(wchar_t* __dest, const char** __src, size_t __nms, size_t __len, mbstate_t* __ps, __locale_t __loc) {
+  __locale_guard __current(__loc);
+  return ::mbsnrtowcs(__dest, __src, __nms, __len, __ps); // non-standard
+}
+
+inline _LIBCPP_HIDE_FROM_ABI size_t
+__mbrtowc(wchar_t* __pwc, const char* __s, size_t __n, mbstate_t* __ps, __locale_t __loc) {
+  __locale_guard __current(__loc);
+  return std::mbrtowc(__pwc, __s, __n, __ps);
+}
+
+inline _LIBCPP_HIDE_FROM_ABI int __mbtowc(wchar_t* __pwc, const char* __pmb, size_t __max, __locale_t __loc) {
+  __locale_guard __current(__loc);
+  return std::mbtowc(__pwc, __pmb, __max);
+}
+
+inline _LIBCPP_HIDE_FROM_ABI size_t __mbrlen(const char* __s, size_t __n, mbstate_t* __ps, __locale_t __loc) {
+  __locale_guard __current(__loc);
+  return std::mbrlen(__s, __n, __ps);
+}
+
+inline _LIBCPP_HIDE_FROM_ABI size_t
+__mbsrtowcs(wchar_t* __dest, const char** __src, size_t __len, mbstate_t* __ps, __locale_t __loc) {
+  __locale_guard __current(__loc);
+  return std::mbsrtowcs(__dest, __src, __len, __ps);
+}
+#  endif // _LIBCPP_HAS_WIDE_CHARACTERS
+#endif   // _LIBCPP_BUILDING_LIBRARY
+
+#ifndef _LIBCPP_COMPILER_GCC // GCC complains that this can't be always_inline due to C-style varargs
+_LIBCPP_HIDE_FROM_ABI
+#endif
+inline _LIBCPP_ATTRIBUTE_FORMAT(__printf__, 4, 5) int __snprintf(
+    char* __s, size_t __n, __locale_t __loc, const char* __format, ...) {
+  va_list __va;
+  va_start(__va, __format);
+  __locale_guard __current(__loc);
+  int __res = std::vsnprintf(__s, __n, __format, __va);
+  va_end(__va);
+  return __res;
+}
+
+#ifndef _LIBCPP_COMPILER_GCC // GCC complains that this can't be always_inline due to C-style varargs
+_LIBCPP_HIDE_FROM_ABI
+#endif
+inline _LIBCPP_ATTRIBUTE_FORMAT(__printf__, 3, 4) int __asprintf(
+    char** __s, __locale_t __loc, const char* __format, ...) {
+  va_list __va;
+  va_start(__va, __format);
+  __locale_guard __current(__loc);
+  int __res = ::vasprintf(__s, __format, __va); // non-standard
+  va_end(__va);
+  return __res;
+}
+} // namespace __locale
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___LOCALE_DIR_SUPPORT_HAIKU_H
diff --git a/lib/libcxx/src/include/config_elast.h b/lib/libcxx/src/include/config_elast.h
index daec2429de8eb5953ac48425dd0a8568bb2cb2ea..927a0a9ce84facf64dd1c37a3241e4b9cc0d0869 100644
--- a/lib/libcxx/src/include/config_elast.h
+++ b/lib/libcxx/src/include/config_elast.h
@@ -33,6 +33,9 @@
 // No _LIBCPP_ELAST needed on WASI
 #elif defined(__EMSCRIPTEN__)
 // No _LIBCPP_ELAST needed on Emscripten
+// zig patch: haiku support
+#elif defined(__HAIKU__)
+// No _LIBCPP_ELAST needed on Haiku
 #elif defined(__linux__) || _LIBCPP_HAS_MUSL_LIBC
 #  define _LIBCPP_ELAST 4095
 #elif defined(__APPLE__)
diff --git a/lib/libcxxabi/include/cxxabi.h b/lib/libcxxabi/include/cxxabi.h
index c65e353d68daf5237e550e34522dec6d838780d0..7b88011c4234e6fc92577a92f2a1810c16ceb55b 100644
--- a/lib/libcxxabi/include/cxxabi.h
+++ b/lib/libcxxabi/include/cxxabi.h
@@ -179,7 +179,8 @@ __cxa_decrement_exception_refcount(void *primary_exception) _LIBCXXABI_NOEXCEPT;
 extern _LIBCXXABI_FUNC_VIS bool __cxa_uncaught_exception() _LIBCXXABI_NOEXCEPT;
 extern _LIBCXXABI_FUNC_VIS unsigned int __cxa_uncaught_exceptions() _LIBCXXABI_NOEXCEPT;
 
-#if defined(__linux__) || defined(__Fuchsia__)
+// zig patch: haiku support
+#if defined(__linux__) || defined(__Fuchsia__) || defined(__HAIKU__)
 // Linux and Fuchsia TLS support. Not yet an official part of the Itanium ABI.
 // https://sourceware.org/glibc/wiki/Destructor%20support%20for%20thread_local%20variables
 extern _LIBCXXABI_FUNC_VIS int __cxa_thread_atexit(void (*)(void *), void *,
diff --git a/lib/libcxxabi/src/cxa_thread_atexit.cpp b/lib/libcxxabi/src/cxa_thread_atexit.cpp
index 402a52c741012d168a7ab0d3a839e7a765aee7e7..bf3351f864c7257f6c714c78b5c7f61bb2d50463 100644
--- a/lib/libcxxabi/src/cxa_thread_atexit.cpp
+++ b/lib/libcxxabi/src/cxa_thread_atexit.cpp
@@ -106,7 +106,8 @@ namespace {
 
 #endif // HAVE___CXA_THREAD_ATEXIT_IMPL
 
-#if defined(__linux__) || defined(__Fuchsia__)
+// zig patch: haiku support
+#if defined(__linux__) || defined(__Fuchsia__) || defined(__HAIKU__)
 extern "C" {
 
   _LIBCXXABI_FUNC_VIS int __cxa_thread_atexit(Dtor dtor, void* obj, void* dso_symbol) throw() {