'Aqualung' was the fourth studio album by the rock band Jethro Tull. First released in 1971, 'Aqualung,' despite the band's disapproval, is regarded as a concept album featuring a central theme of "the distinction between religion and God"

Recorded at Island Records' studio in London, it was their first album with John Evan as a full-time member, their first with new bassist Jeffrey Hammond and last album featuring Clive Bunker on drums. Something of a departure from the band's previous work, the album features more acoustic material than previous releases; and—inspired by photographs of homeless people on the Thames Embankment taken by singer Ian Anderson's wife Jennie—contains a number of recurring themes, addressing religion along with Anderson's own personal experiences.

Aqualung has sold more than 7 million units worldwide according to Anderson, and is thus Jethro Tull's best selling album.