Regan 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. She was portrayed by Linda Blair in both films and by Geena Davis in the television series The Exorcist (2016–2017) . In the first film, Regan becomes possessed by the ancient demon Pazuzu, and her mother, Chris, consults Fr. Damien Karras and begs him to evaluate Regan for an exorcism. While Karras is initially skeptical, he slowly becomes convinced that she is indeed possessed by the demon, and eventually calls for an exorcism. After the exorcism, Regan is restored to her old self and given the medallion of Saint Joseph for protection.

In the sequel Exorcist II: The Heretic, which takes place four years after the events in The Exorcist, Regan is 16 years old, living in New York City and undergoing psychiatric therapy, claiming to remember nothing about her plight in Washington, D.C. while her psychiatrist believes her memories are only buried or repressed. As the story progresses, Regan is revealed to have psychic healing powers (the reason why the demon attacked her previously). Regan, with the help of the priests Tomas Ortega and Marcus Keane, finds the strength to once again exorcise the demon from her body and soul, but he retaliates by breaking her back, confining her to a wheelchair.

In The Exorcist: Believer, Regan comes to the hospital to comfort her injured mother, Chris, but it is unlikely that all is forgiven already. After all, Regan did not have any memory of the exorcism when The Exorcist ended, so Chris book could have been how she learned about the entire experience. The likelihood that Chris played a part in Regan learning about these events and forcing her to relive them in a public manner explains the distance between them. Regans story is left in a rather happy place in the original movie, as she does not have any memories of the exorcism or possession. The Exorcist: Believer suggests that she does come to learn about the experience somehow, but whether her memories return or that is strictly through Chris book is unclear. It is possible that Regan was hiding for the last 30 years before The Exorcist: Believer.