William Peter Blatty (January 7, 1928 – January 12, 2017) was an American writer, director and producer. He is best known for his 1971 novel The Exorcist and for his screenplay for the 1973 film adaptation. Blatty won an Academy Award for Best Adapted Screenplay for The Exorcist, and was nominated for Best Picture as its producer. The film also earned Blatty a Golden Globe Award for Best Motion Picture – Drama as producer.

Born and raised in New York City, Blatty received his bachelor's degree in English from Georgetown University in 1950, and his master's degree in English literature from the George Washington University. Following completion of his master's degree in 1954, he joined the United States Air Force and served in the Psychological Warfare Division where he attained the rank of first lieutenant. After service in the air force, he worked for the United States Information Agency in Beirut.

After the success of The Exorcist, Blatty reworked his 1966 novel Twinkle, Twinkle, "Killer" Kane! into a new novel titled The Ninth Configuration, published in 1978. He went on to adapt the novel into the 1980 film, which was also his directorial debut. At the 38th Golden Globe Awards, the film won Best Screenplay and was nominated for Best Picture.

Blatty refused to have any involvement with the first sequel to The Exorcist; it was critically panned. He directed the second sequel, The Exorcist III (1990), which he adapted from his 1983 novel Legion. His second film as a director, The Exorcist III was his final directorial credit and final screenplay credit. Some of his later novels include Elsewhere (2009), Dimiter (2010) and Crazy (2010).

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