Martin Lancelot Barre (/bɑːr/; born 17 November 1946, Kings Heath, Birmingham, West Midlands, England) is an English rock musician.

Barre was the guitarist for rock band Jethro Tull, starting with the band's second album in 1969. Barre once said that he tried not to listen to other guitarists so that he would not be influenced by them. He said he never took guitar lessons so that he would not sound like other players. He has also played the flute, both on-stage for Jethro Tull and in his own solo work.