William Peter Blatty (born January 7, 1928) is an American writer and filmmaker. The novel The Exorcist, written in 1971, is his magnum opus; he also penned the subsequent screenplay version of the film, for which he won an Academy Award. He also wrote and directed the sequel The Exorcist III.
His most recent works include the novels Elsewhere (2009), Dimiter (2010) and Crazy (2010). He is also featured in the upcoming 2012 Smoke And Mirrors anthology, featuring the teleplay "Hell Hospital" and the treatment "Faith".