The Exorcist is an American media franchise that originated with William Peter Blatty's 1971 horror novel of the same name and most prominently featured in a 1973 film adapted from the novel, and many subsequent prequels and sequels. All of these installments focus on fictional accounts of people possessed by Pazuzu, the main antagonist of the series, and the efforts of religious authorities to counter this possession.

The Exorcist is a 1971 novel by American writer William Peter Blatty. The book details the demonic possession of twelve-year-old Regan MacNeil, the daughter of a famous actress, and the two priests who attempt to exorcise the demon. It was published by Harper & Row.

The novel was inspired by a 1949 case of demonic possession and exorcism that Blatty heard about while he was a student in the class of 1950 at Georgetown University.[1] As a result, the novel takes place in Washington D.C. near the campus of Georgetown University. In September 2011, the novel was reprinted by Harper Collins to celebrate its fortieth anniversary, with slight revisions made by Blatty as well as interior title artwork by Jeremy Caniglia.

Legion is the 1983 follow-up to the Exorcist novel. It was made into the movie The Exorcist III in 1990. Like The Exorcist, it involves demonic possession. The book was the focus of a court case over its exclusion from The New York Times Best Seller list.

Blatty based aspects of the Gemini Killer on the real-life Zodiac Killer,[2] who, in a January 1974 letter to the San Francisco Chronicle, had praised the original Exorcist film as "the best satirical comedy that I have ever seen".[3]