Darcy O'Brien (July 16, 1939, Los Angeles – March 2, 1998, Tulsa) was an award-winning author of fiction and literary criticism, most well known for his work in the genre of true crime. His first novel, A Way of Life, Like Any Other, was a fictionalized account of his childhood in Hollywood. In 1985, he wrote a book about the Hillside Stranglers entitled Two of a Kind: The Hillside Stranglers which was adapted into a made-for-television film called The Case of the Hillside Stranglers starring Richard Crenna.
Darcy O'Brien was born in Los Angeles, the son of Hollywood silent film actor George O'Brien and actress Marguerite Churchill, a frequent co-star of John Wayne.
O'Brien attended Princeton University and University of Cambridge, and received a master's degree and doctorate from the University of California, Berkeley. From 1965 to 1978 he was a professor of English at Pomona College. In 1978 he moved to Tulsa, and taught at the University of Tulsa until 1995.
O'Brien was married three times and had one daughter named Molly O'Brien. His sister is Orin O'Brien, a double bassist and member of the New York Philharmonic.
O'Brien died of a heart attack in Tulsa on March 2, 1998.