diff -r 669d6b5c1734 Lib/test/test_textwrap.py
--- a/Lib/test/test_textwrap.py	Sat Jul 18 16:31:29 2015 -0700
+++ b/Lib/test/test_textwrap.py	Sun Jul 19 02:40:18 2015 +0000
@@ -443,6 +443,10 @@
 Did you say "supercalifragilisticexpialidocious?"
 How *do* you spell that odd word, anyways?
 '''
+        self.text_cjk = '''\
+Did you say "いろはにほへとちりぬるをいろはにほ?"
+How りぬ るをいろはにほり ぬるは, anyways?
+'''.decode('utf-8')
 
     def test_break_long(self):
         # Wrap text with long words and lots of punctuation
@@ -455,6 +459,14 @@
         self.check_wrap(self.text, 50,
                         ['Did you say "supercalifragilisticexpialidocious?"',
                          'How *do* you spell that odd word, anyways?'])
+        self.check_wrap(self.text_cjk, 30,
+                        ['Did you say "いろはにほへとち'.decode('utf-8'),
+                         'りぬるをいろはにほ?" How りぬ'.decode('utf-8'),
+                         'るをいろはにほり ぬるは,'.decode('utf-8'),
+                         'anyways?'])
+        self.check_wrap(self.text_cjk, 50,
+                        ['Did you say "いろはにほへとちりぬるをいろはにほ?"'.decode('utf-8'),
+                         'How りぬ るをいろはにほり ぬるは, anyways?'.decode('utf-8')])
 
         # SF bug 797650.  Prevent an infinite loop by making sure that at
         # least one character gets split off on every pass.
diff -r 669d6b5c1734 Lib/textwrap.py
--- a/Lib/textwrap.py	Sat Jul 18 16:31:29 2015 -0700
+++ b/Lib/textwrap.py	Sun Jul 19 02:40:18 2015 +0000
@@ -7,7 +7,7 @@
 
 __revision__ = "$Id$"
 
-import string, re
+import string, re, unicodedata
 
 try:
     _unicode = unicode
@@ -225,8 +225,9 @@
         # If we're allowed to break long words, then do so: put as much
         # of the next chunk onto the current line as will fit.
         if self.break_long_words:
-            cur_line.append(reversed_chunks[-1][:space_left])
-            reversed_chunks[-1] = reversed_chunks[-1][space_left:]
+            chunk_start, chunk_end = slice_cjk(reversed_chunks[-1], space_left)
+            cur_line.append(chunk_start)
+            reversed_chunks[-1] = chunk_end
 
         # Otherwise, we have to preserve the long word intact.  Only add
         # it to the current line if there's nothing already there --
@@ -283,7 +284,7 @@
                 del chunks[-1]
 
             while chunks:
-                l = len(chunks[-1])
+                l = len_cjk(chunks[-1])
 
                 # Can at least squeeze this chunk onto the current line.
                 if cur_len + l <= width:
@@ -296,7 +297,7 @@
 
             # The current line is full, and the next chunk is too big to
             # fit on *any* line (not just this one).
-            if chunks and len(chunks[-1]) > width:
+            if chunks and len_cjk(chunks[-1]) > width:
                 self._handle_long_word(chunks, cur_line, cur_len, width)
 
             # If the last chunk on this line is all whitespace, drop it.
@@ -419,6 +420,31 @@
         text = re.sub(r'(?m)^' + margin, '', text)
     return text
 
+
+# -- CJK support ------------------------------------------------------
+
+def len_cjk(text):
+    if isinstance(text, str):
+        return len(text)
+    l = 0
+    for char in text:
+        if unicodedata.east_asian_width(unicode(char)) in ('F', 'W'):
+            l = l + 2
+        else:
+            l = l + 1
+    return l
+
+def slice_cjk(text, space_left):
+    if isinstance(text, str):
+        return text[:space_left], text[space_left:]
+    i = 1
+    while len_cjk(text[:i]) <= space_left:
+        # <= and index i-1
+        # to catch the last double length char of odd line
+        i = i + 1
+    return text[:i-1], text[i-1:]
+
+
 if __name__ == "__main__":
     #print dedent("\tfoo\n\tbar")
     #print dedent("  \thello there\n  \t  how are you?")
diff -r 669d6b5c1734 Misc/ACKS
--- a/Misc/ACKS	Sat Jul 18 16:31:29 2015 -0700
+++ b/Misc/ACKS	Sun Jul 19 02:40:18 2015 +0000
@@ -452,6 +452,7 @@
 Santiago Gala
 Yitzchak Gale
 Matthew Gallagher
+Florent Gallaire
 Quentin Gallet-Gilles
 Riccardo Attilio Galli
 Raymund Galvin