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',