Windows Media Player (WMP) is a digital media player and media library application developed by Microsoft that is used for playing audio, video and viewing images on personal computers running the Microsoft Windows operating system, as well as on Pocket PC and Windows Mobile-based devices. Editions of Windows Media Player were also released for Mac OS, Mac OS X and Solaris, but have since been discontinued.

In addition to being a media player, Windows Media Player includes the ability to rip music from and copy music to compact discs, build Audio CDs in recordable discs and synchronize content with a digital audio player (MP3 player) or other mobile devices, and enables users to purchase or rent music from a number of online music stores.

Windows Media Player replaced an earlier piece of software simply called Media Player, adding features beyond simple video or audio playback.

The default file formats are Windows Media Video (WMV), Windows Media Audio (WMA), and Advanced Systems Format (ASF), and supports its own XML based playlist format called Windows Playlist (WPL). The Zune software which actually is a modified version of Windows Media Player additionally supports AAC (Advanced Audio Coding) audio, MPEG-4 and H.264 video formats out-of-the-box.