Windows Media Video (WMV) is a video compression format for several proprietary codecs developed by Microsoft. The original video format, known as WMV, was originally designed for Internet streaming applications, as a competitor to RealVideo. The other formats, such as WMV Screen and WMV Image, cater for specialized content. Through standardization from the Society of Motion Picture and Television Engineers (SMPTE), WMV 9 hasgained adoption for physical-delivery formats such as HD DVD and Blu-ray Disc.

In 2003, Microsoft drafted a video codec specification based on its WMV 9 codec and submitted it to SMPTE for standardization. The standard was officially approved in March 2006 as SMPTE 421M, better known as VC-1, thus making the WMV 9 format an open standard. Since then, VC-1 has become one of the three allowable video formats for the Blu-ray format, along with H.262/MPEG-2 Part 2 and H.264.

Windows Media Video (WMV) is the most recognized video format within the WMV family. Usage of the term WMV often refers to the Microsoft Windows Media Video codec only. Its main competitors are MPEG-4 AVC, AVS, RealVideo, and MPEG-4 ASP.

The first version of the codec, WMV 7, was introduced in 1999, and was built upon Microsoft's implementation of MPEG-4 Part 2. Continued proprietary development led to newer versions of the codec, but the bit stream syntax was not frozen until WMV 9.

While all versions of WMV support variable bit rate, average bit rate, and constant bit rate, WMV 9 introduced several important features includingnative support for interlaced video, non-square pixels, and frame interpolation. WMV 9 also introduced a new profile titled Windows Media Video 9 Professional, which is activated automatically whenever the video resolution exceeds 300,000 pixels (e.g., 528x576, 640x480 or 768x432 and beyond) and the bitrate 1000 kbit/s. It is targeted towards high-definition video content, at resolutions such as 720p and 1080p.