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 has gained 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 mandatory video formats for the BD-ROM specifications.

A WMV file is in most circumstances encapsulated in the Advanced Systems Format (ASF) container format. The file extension .WMV typically describes ASF files that use Windows Media Video codecs. The audio codec used in conjunction with Windows Media Video is typically some version of Windows Media Audio, or in rarer cases, the deprecated Sipro ACELP.net audio codec. Microsoft recommends that ASF files containing non-Windows Media codecs use the generic .ASF file extension.

Windows Media is a multimedia framework for media creation and distribution for Microsoft Windows. It consists of a software development kit (SDK) with several application programming interfaces (API) and a number of prebuilt technologies, and is the replacement of NetShow technologies.

The Windows Media SDK is being replaced by Media Foundation.