Index: include/__config
===================================================================
--- include/__config
+++ include/__config
@@ -882,6 +882,8 @@
     defined(__CloudABI__) || \
     defined(__sun__)
 #  define _LIBCPP_HAS_THREAD_API_PTHREAD
+# elif defined(_WIN32)
+#  define _LIBCPP_HAS_THREAD_API_WIN32
 # else
 #  error "No thread API"
 # endif // _LIBCPP_HAS_THREAD_API
Index: include/__threading_support
===================================================================
--- include/__threading_support
+++ include/__threading_support
@@ -30,6 +30,237 @@
 #if defined(_LIBCPP_HAS_THREAD_API_EXTERNAL) && \
     __libcpp_has_include(<__external_threading>)
 #include <__external_threading>
+#elif defined(_WIN32) && defined(_LIBCPP_HAS_THREAD_API_WIN32)
+#define WIN32_LEAN_AND_MEAN
+#define VC_EXTRA_LEAN
+#include <Windows.h>
+#include <process.h>
+#include <fibersapi.h>
+
+// Mutex
+typedef CRITICAL_SECTION __libcpp_mutex_t;
+#define _LIBCPP_MUTEX_INITIALIZER                                              \
+  { (PRTL_CRITICAL_SECTION_DEBUG) - 1, -1, 0, 0, 0, 0 }
+
+inline _LIBCPP_INLINE_VISIBILITY
+int __libcpp_recursive_mutex_init(__libcpp_mutex_t *__m);
+
+inline _LIBCPP_INLINE_VISIBILITY
+int __libcpp_mutex_lock(__libcpp_mutex_t *__m);
+
+inline _LIBCPP_INLINE_VISIBILITY
+int __libcpp_mutex_unlock(__libcpp_mutex_t *__m);
+
+inline _LIBCPP_INLINE_VISIBILITY
+int __libcpp_mutex_destroy(__libcpp_mutex_t *__m);
+
+// Condition Variable
+typedef CONDITION_VARIABLE __libcpp_condvar_t;
+#define _LIBCPP_CONDVAR_INITIALIZER CONDITION_VARIABLE_INIT
+
+inline _LIBCPP_INLINE_VISIBILITY
+int __libcpp_condvar_signal(__libcpp_condvar_t *__cv);
+
+inline _LIBCPP_INLINE_VISIBILITY
+int __libcpp_condvar_broadcast(__libcpp_condvar_t *__cv);
+
+inline _LIBCPP_INLINE_VISIBILITY
+int __libcpp_condvar_wait(__libcpp_condvar_t *__cv, __libcpp_mutex_t *__m);
+
+inline _LIBCPP_INLINE_VISIBILITY
+int __libcpp_condvar_timedwait(__libcpp_condvar_t *__cv, __libcpp_mutex_t *__m,
+                               timespec *__tm);
+
+inline _LIBCPP_INLINE_VISIBILITY
+int __libcpp_condvar_destroy(__libcpp_condvar_t *__cv);
+
+// Thread ID
+typedef DWORD __libcpp_thread_id;
+
+inline _LIBCPP_INLINE_VISIBILITY
+bool __libcpp_thread_id_equal(__libcpp_thread_id __lhs,
+                              __libcpp_thread_id __rhs);
+
+inline _LIBCPP_INLINE_VISIBILITY
+bool __libcpp_thread_id_less(__libcpp_thread_id __lhs,
+                             __libcpp_thread_id __rhs);
+
+// Thread
+typedef HANDLE __libcpp_thread_t;
+
+inline _LIBCPP_INLINE_VISIBILITY
+int __libcpp_thread_create(__libcpp_thread_t *__t, void *(*__func)(void *),
+                           void *__arg);
+
+inline _LIBCPP_INLINE_VISIBILITY
+__libcpp_thread_id __libcpp_thread_get_current_id();
+
+inline _LIBCPP_INLINE_VISIBILITY
+__libcpp_thread_id __libcpp_thread_get_id(const __libcpp_thread_t *_t);
+
+inline _LIBCPP_INLINE_VISIBILITY
+int __libcpp_thread_join(__libcpp_thread_t *__t);
+
+inline _LIBCPP_INLINE_VISIBILITY
+int __libcpp_thread_detach(__libcpp_thread_t *__t);
+
+inline _LIBCPP_INLINE_VISIBILITY
+void __libcpp_thread_yield();
+
+// Thread Local Storage
+typedef DWORD __libcpp_tls_key;
+
+inline _LIBCPP_INLINE_VISIBILITY
+int __libcpp_tls_create(__libcpp_tls_key *__key, void (*__at_exit)(void *));
+
+inline _LIBCPP_INLINE_VISIBILITY
+void *__libcpp_tls_get(__libcpp_tls_key __key);
+
+inline _LIBCPP_INLINE_VISIBILITY
+void __libcpp_tls_set(__libcpp_tls_key __key, void *__p);
+
+
+// Mutex
+int __libcpp_recursive_mutex_init(__libcpp_mutex_t *__m)
+{
+  InitializeCriticalSection(__m);
+  return 0;
+}
+
+int __libcpp_mutex_lock(__libcpp_mutex_t *__m)
+{
+  EnterCriticalSection(__m);
+  return 0;
+}
+
+int __libcpp_mutex_trylock(__libcpp_mutex_t *__m)
+{
+  return TryEnterCriticalSection(__m);
+}
+
+int __libcpp_mutex_unlock(__libcpp_mutex_t *__m)
+{
+  LeaveCriticalSection(__m);
+  return 0;
+}
+
+int __libcpp_mutex_destroy(__libcpp_mutex_t *__m)
+{
+  DeleteCriticalSection(__m);
+  return 0;
+}
+
+// Condition Variable
+int __libcpp_condvar_signal(__libcpp_condvar_t *__cv)
+{
+  WakeConditionVariable(__cv);
+  return 0;
+}
+
+int __libcpp_condvar_broadcast(__libcpp_condvar_t *__cv)
+{
+  WakeAllConditionVariable(__cv);
+  return 0;
+}
+
+int __libcpp_condvar_wait(__libcpp_condvar_t *__cv, __libcpp_mutex_t *__m)
+{
+  SleepConditionVariableCS(__cv, __m, INFINITE);
+  return 0;
+}
+
+int __libcpp_condvar_timedwait(__libcpp_condvar_t *__cv, __libcpp_mutex_t *__m,
+                               timespec *__ts)
+{
+  using namespace _VSTD::chrono;
+  auto timeout = seconds(__ts->tv_sec) + nanoseconds(__ts->tv_nsec);
+  // TODO(compnerd) handle timeouts < 10ms
+  // TODO(compnerd) handle spurious timeout
+  if (!SleepConditionVariableCS(__cv, __m,
+                                duration_cast<milliseconds>(timeout).count()))
+    return GetLastError();
+  return 0;
+}
+
+int __libcpp_condvar_destroy(__libcpp_condvar_t *__cv)
+{
+  static_cast<void>(__cv);
+  return 0;
+}
+
+// Thread ID
+bool __libcpp_thread_id_equal(__libcpp_thread_id __lhs,
+                              __libcpp_thread_id __rhs)
+{
+  return __lhs == __rhs;
+}
+
+bool __libcpp_thread_id_less(__libcpp_thread_id __lhs, __libcpp_thread_id __rhs)
+{
+  return __lhs < __rhs;
+}
+
+// Thread
+int __libcpp_thread_create(__libcpp_thread_t *__t,
+                           unsigned int (* WINAPI __func)(void *), void *__arg)
+{
+  *__t =
+      reinterpret_cast<HANDLE>(_beginthreadex(NULL, 0, __func, __arg, 0, NULL));
+  if (*__t)
+    return 0;
+  return GetLastError();
+}
+
+__libcpp_thread_id __libcpp_thread_get_current_id()
+{
+  return GetCurrentThreadId();
+}
+
+__libcpp_thread_id __libcpp_thread_get_id(const __libcpp_thread_t *__t)
+{
+  return GetThreadId(*__t);
+}
+
+int __libcpp_thread_join(__libcpp_thread_t *__t)
+{
+  if (WaitForSingleObjectEx(*__t, INFINITE, FALSE) == WAIT_FAILED)
+    return GetLastError();
+  if (!CloseHandle(*__t))
+    return GetLastError();
+  return 0;
+}
+
+int __libcpp_thread_detach(__libcpp_thread_t *__t)
+{
+  if (!CloseHandle(*__t))
+    return GetLastError();
+  return 0;
+}
+
+void __libcpp_thread_yield()
+{
+  SwitchToThread();
+}
+
+// Thread Local Storage
+int __libcpp_tls_create(__libcpp_tls_key *__key, void (* WINAPI __at_exit)(void *))
+{
+  *__key = FlsAlloc(__at_exit);
+  if (*__key == FLS_OUT_OF_INDEXES)
+    return GetLastError();
+  return 0;
+}
+
+void *__libcpp_tls_get(__libcpp_tls_key __key)
+{
+  return FlsGetValue(__key);
+}
+
+void __libcpp_tls_set(__libcpp_tls_key __key, void *__p)
+{
+  FlsSetValue(__key, __p);
+}
+
 #else
 #include <pthread.h>
 #include <sched.h>
Index: src/algorithm.cpp
===================================================================
--- src/algorithm.cpp
+++ src/algorithm.cpp
@@ -48,7 +48,10 @@
 template unsigned __sort5<__less<long double>&, long double*>(long double*, long double*, long double*, long double*, long double*, __less<long double>&);
 
 #ifndef _LIBCPP_HAS_NO_THREADS
-_LIBCPP_SAFE_STATIC static __libcpp_mutex_t __rs_mut = _LIBCPP_MUTEX_INITIALIZER;
+#if !defined(_WIN32)
+_LIBCPP_SAFE_STATIC
+#endif
+static __libcpp_mutex_t __rs_mut = _LIBCPP_MUTEX_INITIALIZER;
 #endif
 unsigned __rs_default::__c_ = 0;
 
Index: src/memory.cpp
===================================================================
--- src/memory.cpp
+++ src/memory.cpp
@@ -155,7 +155,10 @@
 #if !defined(_LIBCPP_HAS_NO_ATOMIC_HEADER)
 
 _LIBCPP_SAFE_STATIC static const std::size_t __sp_mut_count = 16;
-_LIBCPP_SAFE_STATIC static __libcpp_mutex_t mut_back[__sp_mut_count] =
+#if !defined(_WIN32)
+_LIBCPP_SAFE_STATIC
+#endif
+static __libcpp_mutex_t mut_back[__sp_mut_count] =
 {
     _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER,
     _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER,
Index: src/mutex.cpp
===================================================================
--- src/mutex.cpp
+++ src/mutex.cpp
@@ -195,7 +195,10 @@
 // keep in sync with:  7741191.
 
 #ifndef _LIBCPP_HAS_NO_THREADS
-_LIBCPP_SAFE_STATIC static __libcpp_mutex_t mut = _LIBCPP_MUTEX_INITIALIZER;
+#if !defined(_WIN32)
+_LIBCPP_SAFE_STATIC
+#endif
+static __libcpp_mutex_t mut = _LIBCPP_MUTEX_INITIALIZER;
 _LIBCPP_SAFE_STATIC static __libcpp_condvar_t cv = _LIBCPP_CONDVAR_INITIALIZER;
 #endif