Winamp is a media player for Microsoft Windows originally developed by Justin Frankel and Dmitry Boldyrev by their company Nullsoft, which they later sold to AOL in 1999 for $80 million. It was then acquired by Radionomy in 2014. Since version 2 it has been sold as freemium and supports extensibility with plug-ins and skins, and features music visualization, playlist and a media library, supported by a large online community.

Version 1 of Winamp was released in 1997, and quickly grew popular with over 3 million downloads, paralleling the developing trend of MP3 (music) file sharing. Winamp 2.0 was released on September 8, 1998. The 2.x versions were widely used and made Winamp one of the most downloaded Windows applications. By 2000, Winamp had over 25 million registered users and by 2001 it had 60 million users. A poor reception to the 2002 rewrite, Winamp3, was followed by the release of Winamp 5 in 2003, and a later release of version 5.5 in 2007. A now-discontinued version for Android was also released, along with early counterparts for MS-DOS and Macintosh.

Winamp 5.8 (written as Winamp 5.${\displaystyle \infty }$) was leaked to the general public in 2018. The Radionomy team decided to release the version themselves to maintain security levels. Radionomy later announced their intention to eventually release Winamp 6.

Winamp 5.9 was released on 9th September 2022 with mostly technical updates.

Winamp 5.9.1 was released on 22nd December 2022 addressing many old bugs as well as updating the libraries used by both Winamp and its plugins.