Keitel was raised in Brooklyn, NY where his Polish and Romanian immigrant parents owned and operated a luncheonette. At 16, Keitel joined the Marines and served overseas in the Middle East. When he returned home, he began to pursue an interest in acting, training at the famed Actors Studio before eventually landing stage roles in summer stock, repertory, and the fringes of off-off Broadway and community theater. He made his off Broadway debut in Sam Shepard's "Up to Thursday" in 1965 and two years later began his association with director Martin Scorsese when he answered a newspaper ad placed by the then-NYU student director. Scorsese cast him in "Who's That Knocking at My Door?" (1967), which evolved from a student short to Scorsese's well-received feature debut. Keitel went on to make a strong impression with a breakout role as the director's alter ego in "Mean Streets" (1973), though his more introspective character suffered by proximity to Robert De Niro's explosive, out-of-control Johnny Boy.Playing the first of many violent, abusive parts, Keitel reportedly terrified co-star Ellen Burstyn (who won an Oscar for her performance) in Scorsese's "Alice Doesn't Live Here Anymore" (1974). He collaborated with the director again in an unforgettable performance as the pimp (and lover) of teenage runaway prostitute Jodie Foster in "Taxi Driver" (1976); the sheer brilliance of his portrayal lost amidst the kudos for De Niro's tour de force turn as Travis Bickle. Keitel's career promise continued to rise when he landed a leading role in "Apocalypse Now" (1979), but after a falling out with director Francis Ford Coppola, he was replaced by Martin Sheen. Instead of starring in one of the most publicized films of its day, he acted in Ridley Scott's commercially unsuccessful adaptation of Joseph Conrad's "The Duellists" (1977). Keitel was outstanding as a street-smart, aspiring concert pianist who collects debts for his domineering father in James Toback's "Fingers" (1978), zooming in on women and danger with a self-destructive fervor. He also delivered a strong performance as an auto worker up against a corrupt union in Paul Schrader's underrated "Blue Collar" (1978), but he should have avoided the dubious British oater "Eagle's Wing" (1978), directed by Anthony Harvey.During the 1980s Keitel's visibility slipped, and he appeared in character roles for international productions like Bertrand Tavernier's sci-fi offering "Deathwatch" (1980), Tony Richardson's thriller "The Border" (1982), and several titles from Lina Wertmuller including "Vicoli e Deliitti" (1985). Keitel resurfaced in mainstream American cinema in Brian De Palma's unsuccessful stab at a mob comedy, "Wise Guys" (1986), and re-teamed with Toback for a small role in the romantic comedy "The Pick-Up Artist" (1987). But it was Keitel's portrait of a tortured, ambivalent Judas Iscariot in Scorsese's "The Last Temptation of Christ" (1988) that brought the actor back into the general public consciousness, though the controversial but critically well-received film was not popular at the box office. Keitel's co-starring role as a police commissioner brother of Kevin Kline in "The January Man" (1989) was a dud, and the "Chinatown" (1975) sequel "The Two Jakes" (1990) was also an unfortunate flop that threatened to start Keitel's unhappy cycle all over again. The actor rebounded with a meaty role as a sympathetic detective tracking a pair of unwitting outlaws (Susan Sarandon and Geena Davis) in the hit, "Thelma & Louise" (1991). The noir biopic "Bugsy" (1991) reinstated Keitel on the industry's A-list, with a forcefully-drawn performance as Jewish mobster Mickey Cohen that earned him his first Academy Award nomination as Best Supporting Actor. He went on to become a significant figure in 1990s independent filmmaking after proving a godsend to novice writer-director Quentin Tarantino, agreeing to star in and co-produce "Reservoir Dogs" (1992). His involvement enabled the project's budget to soar from $35,000 to $400,000 and attract other major talents that helped make it into an enduring cult classic. Keitel's no-holds-barred performance as the corrupt, substance-abusing antihero of Abel Ferrara's "Bad Lieutenant" (1992) also brought critical kudos and helped boost the reputation of that formerly "B-plus" indie filmmaker. Keitel went on to credit Jane Campion, writer-director of "The Piano" (1993), for helping him alter his tough-guy persona when she cast him in the surprisingly romantic role of Holly Hunter's lover in that film, although his more typical, cool machismo was back on display in Tarantino's galvanizing "Pulp Fiction" (1994). Keitel was perhaps never better than in his subtle, low-key performance as the proprietor of a Brooklyn cigar shop in Wayne Wang's popular art house movie "Smoke" (1995) and its companion piece, "Blue in the Face" (1995). Keitel's stock held strong with another detective role in Spike Lee's critically acclaimed drama "Clockers" (1995), and a strong supporting performance as the patriarch of a vacationing family who find themselves battling vampires in Tarantino and Robert Rodriguez's "From Dusk Till Dawn" (1996). He returned to Europe to play Harry Houdini in the fanciful British period piece "Fairy Tale (1996) and went back to grittier territory in James Mangold's "Cop Land" (1997), an above average police drama anchored by an excellent ensemble cast including Sylvester Stallone and Robert De Niro. Non-studio fare remained closest to Keitel's heart, and his involvement as executive producer and lead role as an ex-Marine in search of redemption in Tony Bui's "Three Seasons" (1999) helped that film win both the Grand Jury Prize and Audience Award at Sundance. He also reteamed that year with Campion on "Holy Smoke" as a cult exit counselor who goes astray while deprogramming Kate Winslet.Keitel was part of the all-star ensemble of the WWII submarine tale "U-571" (2000) before sending up his dark image to play Satan in the Adam Sandler comedic misfire, "Little Nicky" (2000). In 2001, the Goatsingers, a New York-based production company formed by Keitel and Peggy Gormley, produced "The Grey Zone," Tim Blake Nelson's holocaust drama in which Keitel also co-starred alongside David Arquette and Steve Buscemi. Keitel made a return to mainstream commercial fare with "Red Dragon," third in the series of films featuring Anthony Hopkins as Dr. Hannibal Lecter. Keitel served as producer on Juan Gerard's memoir of his Cuban childhood "Dreaming of Julia" (2003) and had a supporting role opposite Nicolas Cage in the Jerry Bruckheimer-produced action blockbuster "National Treasure" (2004), followed by a charismatic role as a villainous music manager in "Be Cool" (2005), the entertaining sequel to "Get Shorty" (1995). In 2006, Keitel starred as an FBI special agent in the highly controversial docudrama miniseries "The Path to 9/11." The following year, he reprised another of his FBI characters in the blockbuster actioner, "National Treasure: Book of Secrets" (2007). In a surprising shift to series television, Keitel was cast in the police drama "Life on Mars" (ABC, 2008-09), where he played a New York police lieutenant, circa the fashion-challenged early 1970s, alongside Michael Imperioli, Gretchen Mol and Lisa Bonet.