Billy Bob Thornton was born on August 4, 1955 in Hot Springs, Arkansas, to Virginia Roberta (Faulkner), a psychic, and William Raymond (Billy Ray) Thornton, an educator, high school history teacher, and basketball coach (now deceased). He is the older brother of James Donald (Jimmy Don) (born in 1958 and now deceased) and John David (born in 1969). He has been married six times and has four children: daughter Amanda Brumfield, with Melissa Lee Gatlin (now Parish); sons William and Harry, both with Pietra Dawn Cherniak; and daughter Bella with Connie Angland.

Billy Bob began his artistic career as a musician, playing drums and singing in a band called Tres Hombres, which once opened for Hank Williams Jr.. In 1981, he moved to Los Angeles with childhood friend Tom Epperson to pursue an acting and writing career. On the side, Billy Bob also sought work as a singer and drummer. He and Epperson tried for years to sell their scripts but no one was buying. During those rough times, Billy Bob neglected his health and subsequently landed in the hospital with heart problems due to malnutrition. In 1992, Billy Bob starred in One False Move (1991), a movie he co-wrote with Epperson. The team finally received attention because of this work, which was very well received in Hollywood. His popularity increased steadily, especially after Sling Blade (1996) which he wrote, directed and in which he starred.