Fancher was born to a Mexican/Danish mother and an American father, a physician, in East Los Angeles, California, USA. At 15, he ran away to Spain to become a flamenco dancer and renamed himself "Mario Montejo". Following the breakup of his marriage to Joann McNabb, he was married to Sue Lyon of Lolita fame from 1963 to 1965.
In 1959, Fancher appeared in the episode "Misfits" of the ABC western television series, The Rebel. In the storyline, Fancher used the name "Bull" with Malcolm Cassell as Billy the Kid and Hal Stalmaster as "Skinny" plot to rob a bank so that they can live thereafter without working. The "Misfits" enlist the help of The Rebel (Nick Adams) in carrying out their doomed scheme.
Fancher then played Deputy Lon Gillis in seven episodes of the ABC western, Black Saddle, with Peter Breck. He guest starred on other westerns, Have Gun, Will Travel, Tate, Stagecoach West, Outlaws, Maverick, Lawman, Temple Houston, Cheyenne (1961 episode "Incident at Dawson Flats"), and also Bonanza (1966 episode "A Dollar's Worth of Trouble").
Fancher appeared in two Troy Donahue films: 1961's Parrish and 1962's Rome Adventure and was cast as Larry Wilson in the 1963 episode "Little Richard" of the CBS anthology series, GE True, hosted by Jack Webb. In 1965, he played the role of Hamp Fisher (a name very similar to his own), in the Perry Mason episode "The Case of the Silent Six." All in all, Fancher played roles in over fifty movies and television shows. During this time, he also had relationships with a variety of women, including Barbara Hershey and Teri Garr. Although he showed interest in screenwriting, it would take until 1977 for Fancher to transition fully into screenwriting. He continues to act occasionally.
After initially failing to convince Philip K. Dick to option Dick's 1968 science fiction novel Do Androids Dream of Electric Sheep? in 1975, Fancher sent his friend Brian Kelly, a prospective film producer. Dick agreed, and Fancher was brought on to write a screenplay before Kelly enlisted the support of producer Michael Deeley. This made Fancher the executive producer, which led to disagreements with the eventual director Ridley Scott who then brought in David Peoples to continue reworking the script. Scott and Fancher had already clashed concerning the movie, as Scott felt the original script did not sufficiently explore the world of the movie, choosing instead to focus on the interior drama. Fancher's rewriting process was too slow for the production crew, which nicknamed him "Happen Faster." The movie was ultimately filmed and released as Blade Runner (1982).
Fancher wrote two films after Blade Runner: The Mighty Quinn (1989) starring Denzel Washington) and The Minus Man (1999) starring Owen Wilson, which he also directed. More recently, he wrote the story and co-wrote with Michael Green the screenplay of Blade Runner 2049 (2017), a sequel to the 1982 film.
In the early 1980s, Fancher wrote and lived outside of Los Angeles in Topanga Canyon. Fancher appeared in a cameo role in the independent film Tonight at Noon (2009), directed by Michael Almereyda and starring Rutger Hauer.
Fancher provided voiceover narration for The Criterion Collection edition DVD extras of the famous film noir adaptations of Ernest Hemingway's short story The Killers, which included the 1946, 1956 and 1964 versions.
He currently resides in the Brooklyn Heights district of New York City. His life was the subject of Escapes, a documentary directed by Michael Almereyda and executive produced by Wes Anderson.Blade Runner (with David Webb Peoples) (1982)
The Mighty Quinn (1989)
The Minus Man (1999) (Director/Writer)
2036: Nexus Dawn (with Michael Green) (2017)
Blade Runner 2049 (with Michael Green) (2017)