Then Play On is the fourth album by blues rock band Fleetwood Mac, first released in September 1969 (see 1969 in music). It is often considered the best album by the Peter Green lineup of the band, and one of the best rock albums of the late 1960s. It was the first of their original albums to feature Danny Kirwan and the last with Peter Green. Jeremy Spencer did not feature on the album apart from "a couple of piano things" Mick Fleetwood told Q Magazine in 1990.

The album has been released with four different song lineups. The current CD lineup compiles all songs from the two US LP lineups, both of which were deviations from the original UK song order.