diff --git a/Doc/library/fnmatch.rst b/Doc/library/fnmatch.rst
index c03a9d3..373399e 100644
--- a/Doc/library/fnmatch.rst
+++ b/Doc/library/fnmatch.rst
@@ -71,6 +71,12 @@ patterns.
    Return the subset of the list of *names* that match *pattern*. It is the same as
    ``[n for n in names if fnmatch(n, pattern)]``, but implemented more efficiently.
 
+.. function:: filterfalse(names, pattern)
+
+   Return the subset of the list of *names* that don't match *pattern*. It is the
+   same as ``[n for n in names if not fnmatch(n, pattern)]``, but implemented more
+   efficiently.
+
 
 .. function:: translate(pattern)
 
diff --git a/Lib/fnmatch.py b/Lib/fnmatch.py
index fd3b514..032ba0f 100644
--- a/Lib/fnmatch.py
+++ b/Lib/fnmatch.py
@@ -14,7 +14,10 @@ import posixpath
 import re
 import functools
 
-__all__ = ["filter", "fnmatch", "fnmatchcase", "translate"]
+__all__ = ["filter", "filterfalse", "fnmatch", "fnmatchcase", "translate"]
+
+# os.path.normcase on posix is NOP. Avoid calling it unnecessarily.
+normalize_case = os.path is not posixpath
 
 def fnmatch(name, pat):
     """Test whether FILENAME matches PATTERN.
@@ -31,8 +34,9 @@ def fnmatch(name, pat):
     if the operating system requires it.
     If you don't want this, use fnmatchcase(FILENAME, PATTERN).
     """
-    name = os.path.normcase(name)
-    pat = os.path.normcase(pat)
+    if normalize_case:
+        name = os.path.normcase(name)
+        pat = os.path.normcase(pat)
     return fnmatchcase(name, pat)
 
 @functools.lru_cache(maxsize=256, typed=True)
@@ -47,19 +51,19 @@ def _compile_pattern(pat):
 
 def filter(names, pat):
     """Return the subset of the list NAMES that match PAT."""
-    result = []
-    pat = os.path.normcase(pat)
+    if normalize_case:
+        pat = os.path.normcase(pat)
+        names = (os.path.normcase(name) for name in names)
     match = _compile_pattern(pat)
-    if os.path is posixpath:
-        # normcase on posix is NOP. Optimize it away from the loop.
-        for name in names:
-            if match(name):
-                result.append(name)
-    else:
-        for name in names:
-            if match(os.path.normcase(name)):
-                result.append(name)
-    return result
+    return [name for name in names if match(name)]
+
+def filterfalse(names, pat):
+    """Return the subset of the list NAMES that don't match PAT."""
+    if normalize_case:
+        pat = os.path.normcase(pat)
+        names = (os.path.normcase(name) for name in names)
+    match = _compile_pattern(pat)
+    return [name for name in names if match(name) is None]
 
 def fnmatchcase(name, pat):
     """Test whether FILENAME matches PATTERN, including case.
diff --git a/Lib/test/test_fnmatch.py b/Lib/test/test_fnmatch.py
index fb74246..93c83db 100644
--- a/Lib/test/test_fnmatch.py
+++ b/Lib/test/test_fnmatch.py
@@ -2,7 +2,7 @@
 
 import unittest
 
-from fnmatch import fnmatch, fnmatchcase, translate, filter
+from fnmatch import fnmatch, fnmatchcase, translate, filter, filterfalse
 
 class FnmatchTestCase(unittest.TestCase):
 
@@ -78,5 +78,11 @@ class FilterTestCase(unittest.TestCase):
         self.assertEqual(filter(['a', 'b'], 'a'), ['a'])
 
 
+class FilterFalseTestCase(unittest.TestCase):
+
+    def test_filterfalse(self):
+        self.assertEqual(filterfalse(['a', 'b'], 'a'), ['b'])
+
+
 if __name__ == "__main__":
     unittest.main()