Jeffrey Hammond, often known by his former stage name Jeffrey Hammond-Hammond, is an English artist and former musician best known for being the bassist of progressive rock band Jethro Tull from 1971 to 1975. With Jethro Tull, Hammond played on some of the band's most successful and well-known albums, including Aqualung (1971) and Thick as a Brick (1972).

Aqualung, released in March 1971 by Chrysalis Records, is the fourth studio album by the rock band Jethro Tull. Though it is generally regarded as a concept album, featuring a central theme of "the distinction between religion and God", the band have said there was no intention to make a concept album, and that only a few songs have a unifying theme. Aqualung's success signalled a turning point in the career of the band, which went on to become a major radio and touring act.