Born and raised in a poor family, the Arkansas native hooked up with future writing partner Tom Epperson when both were children. Thornton began acting while in high school eventually deciding to pursue a full-time performing career. He and Epperson briefly landed in NYC before heading westward to Hollywood. Settling in L.A. in the late 1970s, Thornton worked variously as a rock singer, drummer and actor. He and Epperson wrote scripts which they attempted to sell, although they met with little success initially. After almost ten years in California, the tall, imposing actor made his feature debut in the forgettable direct-to-video release "Hunter's Blood" (filmed in 1986; released in 1988). After a brief turn as a soldier in the Bette Midler vehicle "For the Boys" (1991), Thornton won acclaim for his featured role in Carl Franklin's "One False Move" (1992), which he co-wrote with Epperson. His portrayal of a sociopathic ex-con involved with a black woman (Cynda Williams, who was briefly Thornton's third wife) earned him critical praise. Subsequent feature appearances included supporting roles in Taylor Hackford's "Bound By Honor" (1993), Steven Seagal's directorial debut "On Deadly Ground" (1994) and Jim Jarmusch's "Dead Man" (1995).

Epperson and Thornton's second produced script, "A Family Thing" (1996) garnered attention for its novel story: a white man discovers he has a black half-brother. Actor Robert Duvall brought the germ of the idea to the duo and they in turn fashioned a vehicle for the Oscar-winning actor. The scenario attracted the attention of James Earl Jones who played Duvall's half-brother and offered a star-making role for Irma P Hall as the men's elderly aunt. While the film won reviewers' attention, it set no box-office records. Nevertheless, Thornton's stock in Hollywood was on the rise and later that year, he made his solo screenwriting and directorial debut with "Sling Blade". Appearing onscreen with close-cropped hair, clean-shaven and using slow, raspy vocals punctuated with growls, the actor was barely recognizable as Karl. Although the film alternated between static set pieces (betraying its stage origins) and leisurely-paced scenes, it did feature a strong cast including Lucas Black as a boy who befriends Karl, Natalie Canerday as his mother, John Ritter as a gay man for whom the boy's mother works and especially Dwight Yoakam as the mother's bigoted, abusive boyfriend. Thornton won an Oscar for Best Adapted Screenplay and earned another nomination as Best Actor.

Thornton's career which had gradually been gaining steam exploded with the success of "Sling Blade". He signed a three-picture deal with Miramax and was suddenly one of the most sought-after actors in Hollywood; he was nearly unrecognizable as a psychotic mechanic in Oliver Stone's "U-Turn" before playing a reluctant religious convert in Duvall's "The Apostle", among his 1997 roles. The following year found him as a would-be marijuana kingpin in "Homegrown", a wily political advisor (patterned after real-life spin doctor James Carville) in "Primary Colors" and the Mission Control leader in the summer blockbuster "Armageddon", in addition to playing Bill Paxton's half-wit brother in "A Simple Plan". For the latter, in which he significantly altered his appearance, he earned a Best Supporting Actor Academy Award nomination. Thornton returned to the director's chair to helm "All the Pretty Horses" (2000), which he also adapted from Cormac McCarthy's novel.

On the small screen, Thornton played a character named (appropriately enough) Billy Bob in the busted pilot "Circus" (ABC, 1987) before making his series debut as an ex-greaser who was a surrogate brother to a gang in "The Outsiders" (Fox, 1989). He later carved a niche portraying good ol' boys on such sitcoms as "Evening Shade" (CBS, 1990-93) and the John Ritter-Markie Post vehicle "Hearts Afire" (CBS, 1992-95), both executive produced by friend and fellow Arkansan Harry Thomason. With Epperson, Thornton wrote the HBO movie "Don't Look Back" (1996), directed by Geoff Murphy and starring Eric Stoltz as a musician-addict who stumbles onto drug money with near fatal results.

Thorton's most critically acclaimed role since "Sling Blade" (1996) came when he starred opposite Halle Barry in "Monster's Ball" (2001). Thorton played a hardened jail warden whose life is emerged in his own bitter history and ingrained racism. His character transforms and ends up falling in love with the black woman whose husband he executed. His exquisite portrait of an agonized man trying to embrace love for the first time in years earned him an impressive array of critical plaudits and awards nominations. However, Thornton may have been his own worst enemy when it came to competing for Oscar gold, as he also turned in particularly fine performances in two other films that same year with a comedic turn in Barry Levinson's "Bandits" and sharp, haunting role as the barber drawn into a dark melodrama in the Coen Brothers' loopy noir "The Man Who Wasn't There." Oscar-watchers suggested that Thornton split his own vote among the three roles, resulting in no nominations for the actor.

Thornton's always-reliable acting was also often overshadowed by his bizarre, high-profile relationship with the much-younger actress Angelina Jolie, who became his fifth wife in 2000 after the two met on the 1999 film "Pushing Tin." Their surprise union was characterized by dramatic, obsessive affectations including acquiring tattoos of each other's names and wearing vials of each other's blood when separated. However, the marriage lasted only two years: Jolie filed for divorce in 2002, shortly after adopting a Cambodian orphan who took Thornton's name. On screen in 2002, the actor appeared a pair of low-profile duds, as a philanderer in the offbeat comedy "Waking Up in Reno" which also starred Charlize Theron, Patrick Swayze and Natasha Richardson; and as a parolee who becomes involved with the unknowing wife of the man he killed in "Levity" (2002). But Thornton was in fine, appropriately over-the-top form when he reunited with the Coen Brothers' screwball effort "Intolerable Cruelty" (2003), playing a Texas billionaire who's about to become the latest victim of a gold-digging serial divorcee (Catherine Zeta-Jones); and the actor had a pleasing low-key cameo as a libidinous U.S. president in the witty British romantic comedy "Love, Actually" (2003).

Thornton returned to center stage in peak form in director Terry Zwigoff's deliriously cynical holiday comedy "Bad Santa" (2003)—based on a one-line concept by the Coens—as whiskey-slugging, womanizing safecracker Willie T. Stokes (Thornton) who annually arises from a hazy hibernation to team up with three-foot-tall mastermind Marcus (Tony Cox) and, under the benevolent cover of Santa and Elf, clean out the particular department store in which they happen to be employed. Thornton's performance was a comedic masterstroke, especially when he lets loose with his stinging, profane and sarcastic invective.

He followed up with a measured, intelligent portrayal of high school football coach in the gridiron-obsessed small town of Odessa, Texas, in the hit film "Friday Night Lights" (2004), and then took on a less serious sports minded project when he accepted the role of Little League baseball coach Morris Buttermaker (originally played by Walter Matthau) in the 2005 remake of the classic kids' baseball film "The Bad News Bears." A high school baseball sensation who once earned a Major League tryout in his youth, Thornton was well-suited to the role of the inebriated, washed-up Buttermaker riding herd over a profane team of young misfits, but the film suffered in its adherence to the original and a refusal to sharper the story's edges for a more contemporary audience. Thornton took on his second anti-Christmas-themed film with "The Ice Harvest" (2005), director Harold Ramis' film noir with pitch black comic undercurrents, playing the potentially untrustworthy partner in crime of a mob accountant (John Cusack) who steals a bundle from his boss and endures a perilous Christmas Eve as they prepare to flee.

For his next feature, Thornton wasted his talents as a lifestyle coach for losers in “School for Scoundrels” (2006), a lame and rather predictable comedy from Todd Phillips (“Old School”) about a top secret confidence building class run by a deviant huckster (Thornton) whose tough love tactics and compulsion for prying into his student’s lives leads them to overcome their deep-rooted anxieties to exact revenge. Thornton's roster for 2007 includes “The Astronaut Farmer”, a satirical look at an astronaut forced to leave NASA to save his family’s farm and “Mr. Woodcock”, featuring Thornton as a sadistic gym teacher who terrorizes a best selling self-help author (Seann William Scott) in his youth and is now ready to marry the writer’s widowed mother (Susan Sarandon).