Carl Barât was born in Basingstoke, England on 6 June 1978, and spent most of his childhood in Whitchurch, Hampshire. In a September 2004 interview with Blender Magazine, Barât mentioned having a French, Russian and Polish ethnic background.
As a youth, Barât divided his time between his divorced parents. His father, a former artist, worked in an armaments factory, and his mother, Chrissie, was part of the commune-dwelling counterculture and a member of peace groups such as the Campaign for Nuclear Disarmament. Barât spent part of his childhood living with his mother on a commune in Somerset. He has one sister, actress-turned-singer Lucie Barât, who played Helen's handmaiden in the 2004 film Troy, founded publishing house and artistic organization Little Episodes, and is currently the lead singer of The Fay Wrays. He also has three half-siblings, one step brother and one step sister.
In 1996, Barât was studying for a drama degree at Brunel University at the Twickenham campus in St. Margarets, Twickenham. Although he dropped out halfway through, during his time he became well-acquainted with Peter Doherty's sister, Amy-Jo and through her, Barât met Doherty. They soon developed an intense friendship based on a shared interest in music and songwriting. Barât and Doherty also developed a shared mythology in which they were on a ship called 'The Albion' sailing to 'Arcadia'. After both dropped out of school, they formed The Libertines. The band in its final incarnation included bassist John Hassall and drummer Gary Powell. Barât and Doherty shared songwriting, vocal and guitar duties.