Jethro Tull are an English rock band formed in Luton, Bedfordshire in 1967. Initially playing blues rock, the band soon developed its sound to incorporate elements of British folk music and hard rock to forge a progressive rock signature. The band is led by vocalist/flautist/guitarist Ian Anderson, and featured a revolving door of lineups through the years including significant members such as longtime guitarist Martin Barre, keyboardist John Evan, drummers Clive Bunker, Barriemore Barlow, and Doane Perry, and bassists Glenn Cornick, Jeffrey Hammond, and Dave Pegg.

The group first achieved commercial success in 1969, with the folk-tinged blues album Stand Up, which reached No. 1 in the UK, and they toured regularly in the UK and the US. Their musical style shifted in the direction of progressive rock with the albums Aqualung (1971), Thick as a Brick (1972) and A Passion Play (1973), and shifted again to hard rock mixed with folk rock with Songs from the Wood (1977) and Heavy Horses (1978). Jethro Tull have sold an estimated 60 million albums worldwide, with 11 gold and five platinum albums among them. They have been described by Rolling Stone as "one of the most commercially successful and eccentric progressive rock bands".