In popular music, a cover version or cover song, or simply cover, is a new performance or recording of a previously recorded, commercially released song by someone other than the original artist or composer.

Originally, Billboard and other magazines that track the popularity of musical artists and hit tunes measured the sales success of the published tune, not just recordings of it. Later, they tracked the airplay that songs achieved, some cover versions being more successful recording(s) than the original song(s). Cover versions of well-known, well-liked tunes are often recorded by new or up-and-coming artists to achieve initial success when their unfamiliar original material would be less likely to be successful. Before the onset of rock 'n' roll in the 1950s, songs were published and several records of a song might be brought out by singers of the day, each giving it their individual treatment. Cover versions could also be released as an effort to revive the song's popularity among younger generations of listeners after the popularity of the original version has long since declined over the years.