The Exorcist is a 1973 American supernatural horror film directed by William Friedkin and produced and written for the screen by William Peter Blatty, based on the 1971 novel of the same name by Blatty. The film stars Ellen Burstyn, Max von Sydow, Lee J. Cobb, Kitty Winn, Jack MacGowran (in his final film role), Jason Miller and Linda Blair. It is the first installment in The Exorcist film series, and follows the demonic possession of 12-year-old Regan and her mother's attempt to rescue her through an exorcism conducted by two Roman Catholic priests.

Although the book had been a bestseller, Blatty, who produced, and Friedkin, his choice for director, had difficulty casting the film. After turning down, or being turned down by major stars of the era, they cast in the lead roles the relatively little-known Burstyn, the unknown Blair and Miller, the author of a hit play who had never acted in movies before, casting choices that were vigorously opposed by studio executives at Warner Bros. Pictures. Principal photography was also difficult. Most of the set burned down, and Blair and Burstyn suffered long-term injuries in accidents. Ultimately the film took twice as long to shoot as scheduled and cost more than twice its initial budget.

The Exorcist was released in 24 theaters in the United States and Canada in late December. Audiences flocked to it, waiting in long lines during winter weather, many doing so more than once, despite mixed critical reviews. Some viewers had adverse physical reactions, often fainting or vomiting, to scenes in which the protagonist undergoes a realistic cerebral angiography and violently masturbates with a crucifix. There were reports of heart attacks and miscarriages; a psychiatric journal carried a paper on "cinematic neurosis" triggered by the film. Many children were taken to see the film, leading to charges that the MPAA ratings board had accommodated Warner Brothers by giving the film an R-rating, instead of the X-rating they thought it deserved, in order to ensure its commercial success. Several cities made efforts to ban it outright or prevent children from seeing it.

The cultural conversation around the film, which also encompassed its treatment of Roman Catholicism, helped it become the first horror film to be nominated for the Academy Award for Best Picture, one of ten Academy Awards it was nominated for, winning for Best Adapted Screenplay and Best Sound. It was the highest-grossing R-rated horror film, until the release of It in 2017 (unadjusted for inflation). The Exorcist has had a significant influence on popular culture and has received critical acclaim, with several publications having regarded it as one of the greatest horror films of all time. The English film critic Mark Kermode named it as his "favorite film of all time". In 2010, the Library of Congress selected the film to be preserved as part of its National Film Registry as being "culturally, historically, or aesthetically significant".