diff --git a/Lib/mimetypes.py b/Lib/mimetypes.py
--- a/Lib/mimetypes.py
+++ b/Lib/mimetypes.py
@@ -507,6 +507,7 @@
         '.ustar'  : 'application/x-ustar',
         '.vcf'    : 'text/x-vcard',
         '.wav'    : 'audio/x-wav',
+        '.webm'   : 'video/webm',
         '.wiz'    : 'application/msword',
         '.wsdl'   : 'application/xml',
         '.xbm'    : 'image/x-xbitmap',