William J. Monahan (born November 3, 1960) is an American screenwriter and novelist. His second produced screenplay was The Departed, a film which earned him a WGA award and an Academy award for Best Adapted Screenplay.
Monahan attended the University of Massachusetts at Amherst, where he studied Elizabethan and Jacobean drama. He moved to New York City and contributed to the alternative weekly newspaper New York Press and the magazines Talk, Maxim and Spy. In 1997, Monahan won a Pushcart Prize for his short story "A Relation of Various Accidents Observable in Some Animals Included in Vacuo". Monahan was an editor at Spy during the magazine's final years, where he would come in at the close of the monthly issue to rewrite the articles and improve the jokes.
Monahan wrote a novel titled Light House: A Trifle and Warner Bros. optioned the film rights. In 1999, Talk magazine debuted and Monahan contributed a travelogue on Gloucester, Massachusetts to the first issue. In 2000, Monahan's first novel Light House: A Trifle was finally published and garnered critical acclaim; The New York Times proclaimed "Monahan's cocksure prose gallops along," and BookPage Fiction called Monahan "a worthy successor to Kingsley Amis." In the second half of 2001, Monahan wrote a fictional column at the New York Press under the pseudonym of Claude La Badarian, which ran for 13 weeks.