Born in New York City; educated at Georgetown University and George Washington University. After serving with the Air Force, he began his career as an editor for the US Information Agency, then served as a publicity director for USC and Loyola universities. He had his first novel published in 1963. But it wasn't until 1970 that he scored his first big commercial hit, with The Exorcist, a chilling novel of the supernatural that remained on the best-seller list for more than a year. He later produced and wrote the novel's 1973 screen adaptation, winning an Academy Award for the screenplay. He made an impressive debut as a director with 1980's TWINKLE, TWINKLE KILLER KANE, which he adapted from his novel. In 1990 he also directed EXORCIST III, which he had adapted from his novel Legion. Other notable writing credits (alone or in collaboration) include THE MAN FROM THE DINER'S CLUB (1963), A SHOT IN THE DARK (1964), JOHN GOLDFARB, PLEASE COME HOME and PROMISE HER ANYTHING (both 1965), WHAT DID YOU DO IN THE WAR, DADDY? (1966), GUNN (1967), THE GREAT BANK ROBBERY (1969) and DARLING LILI (1970). Blatty is also the author of Which Way to Mecca, Jack? (1960), Billy Shakespeare! (1965, w. Victoria Chess), I'll Tell Them I Remember You (1974), William Peter Blatty on The Exorcist from Novel to Film (also 1974), Demons Five, Exorcists Nothing: A Fable (1996), The Ninth Configuration (2000, w. Mark Kermode), and If There Were Demons, Then Perhaps There Were Angels: William Peter Blatty's Own Story of The Exorcist (2001, w. Rae Smith).  Nominated for Best Picture 1973: THE EXORCIST - Producer at Hoya  Writing (Best Screenplay Based on Material from Another Medium) 1973: THE EXORCIST 2 nominations, 1 Award