A bootleg recording is an audio and/or video recording of a performance that was not officially released by the artist, or under other legal authority. The process of making and distributing such recordings is known as bootlegging. A great many such recordings are simply copied and traded among fans of the artist without financial exchange, but some bootleggers are able to sell these rarities for profit, sometimes by adding professional-quality sound engineering and packaging to the raw material.

Bootlegs can consist of recordings of live performances, or material created in private or professional recording sessions. Changing technologies have had a great impact on the recording, distribution, and varying profitability of the underground industry.

Although distinct from unauthorized copying ("piracy") and counterfeiting, as it involves material which has never been offered for commercial release, bootlegging is considered infringement in many jurisdictions. The copyrights for the song and the right to authorize recordings often reside with the artist, according to several international copyright treaties. The recording, trading and sale of bootlegs continues to thrive, however, even as artists and record companies attempt to provide "authorized" alternatives to satisfy the demand.