diff --git a/libc/bionic/wcstod.cpp b/libc/bionic/wcstod.cpp
new file mode 100644
index 0000000..eb66ba0
--- /dev/null
+++ b/libc/bionic/wcstod.cpp
@@ -0,0 +1,89 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <wchar.h>
+
+#include <stdlib.h>
+
+#include "local.h"
+
+template <typename float_type> float_type wcstod(const wchar_t* str, wchar_t** end,
+                                                 float_type strtod_fn(const char*, char**)) {
+  // What's the longest span of the input that might be part of the float?
+  size_t max_len = wcsspn(str, L"-+0123456789.xXeEpP()nNaAiIfFtTyY");
+
+  // We know the only valid characters are ASCII, so convert them by brute force.
+  char* ascii_str = new char[max_len + 1];
+  if (!ascii_str) return float_type();
+  for (size_t i = 0; i < max_len; ++i) {
+    ascii_str[i] = str[i] & 0xff;
+  }
+  ascii_str[max_len] = 0;
+
+  // Set up a fake FILE that points to those ASCII characters, for `parsefloat`.
+  FILE f;
+  __sfileext fext;
+  _FILEEXT_SETUP(&f, &fext);
+  f._flags = __SRD;
+  f._bf._base = f._p = reinterpret_cast<unsigned char*>(ascii_str);
+  f._bf._size = f._r = max_len;
+  f._read = [](void*, char*, int) { return 0; }; // aka `eofread`, aka "no more data".
+  f._lb._base = NULL;
+
+  // Ask `parsefloat` to look at the same data more carefully.
+
+  // We can't just do this straight away because we can't construct a suitable FILE*
+  // in the absence of any `fwmemopen` analogous to `fmemopen`. And we don't want to
+  // duplicate the `parsefloat` logic. We also don't want to actually have to have wchar_t
+  // implementations of the ASCII `strtod` logic (though if you were designing a libc
+  // from scratch, you'd probably want to just make that more generic and lose all the
+  // cruft on top).
+  size_t actual_len = parsefloat(&f, ascii_str, ascii_str + max_len);
+
+  // Finally let the ASCII conversion function do the work.
+  char* ascii_end;
+  float_type result = strtod_fn(ascii_str, &ascii_end);
+  if (ascii_end != ascii_str + actual_len) abort();
+
+  if (end) *end = const_cast<wchar_t*>(str) + actual_len;
+
+  delete[] ascii_str;
+  return result;
+}
+
+float wcstof(const wchar_t* s, wchar_t** end) {
+  return wcstod<float>(s, end, strtof);
+}
+
+double wcstod(const wchar_t* s, wchar_t** end) {
+  return wcstod<double>(s, end, strtod);
+}
+
+long double wcstold(const wchar_t* s, wchar_t** end) {
+  return wcstod<long double>(s, end, strtold);
+}