The Exorcist is a 1971 horror novel by American writer William Peter Blatty. The book details the demonic possession of eleven-year-old Regan MacNeil, the daughter of a famous actress, and the two priests who attempt to exorcise the demon. Published by Harper & Row, the novel was the basis of a highly successful film adaptation released two years later, whose screenplay was also written and produced by Blatty, and part of The Exorcist franchise.