Regan Teresa MacNeil is a fictional character in the 1971 novel The Exorcist and one of the supporting characters in its 1973 film adaptation and the 1977 film Exorcist II: The Heretic, while being one of the main protagonists in the first season of the television series The Exorcist (2016–2017). She was portrayed by Linda Blair in both films and by Geena Davis in the television series. Blair reprised the role in the 2023 film, The Exorcist: Believer.

The Exorcist is a 1971 horror novel written by American writer William Peter Blatty and published by Harper & Row. 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. The novel was the basis of a highly successful film adaptation released two years later, whose screenplay was also written and produced by Blatty. More movies and books were eventually added to The Exorcist franchise.