WMV (Windows Media Video) is a video compression format developed by Microsoft and originally designed for Internet streaming applications as a competitor to RealVideo.

A WMV file is in most cases encapsulated in the Advanced System Format (.ASF) container format. The file extension .WMV typically describes an .ASF file that uses Windows Media Video codecs.

The audio codec used in conjunction with Windows Media Video is some version of Windows Media Audio and in rare cases other audio codecs. It also can be put in Matroska or AVI container format. The files in this case are .MKV and .AVI respectively.

The main advantage of the format is that it allows large video files to be compressed yet retaining considerably high quality. Many on-line radio stations use it to stream continuous data flow.