Caligula (Italian: Caligola) is a 1979 erotic historical drama film about the rise and fall of Roman Emperor Caligula. The film stars Malcolm McDowell in the title role, alongside Teresa Ann Savoy, Helen Mirren, Peter O'Toole, John Steiner, and John Gielgud.

Original screenwriter Gore Vidal and film director Tinto Brass both disavowed the extensive changes to their contributions, with Brass dismissed prior to editing. Financier/producer Bob Guccione, founder of Penthouse magazine, engaged Giancarlo Lui to film post-production scenes featuring hardcore sex, significantly altering the film's tone and style.

Initially released to Italian cinemas in 1979, then screened in America the following year, Caligula was met with legal issues and controversies over its violent and sexual content. Different abridged versions were released worldwide, while its uncut form remains banned in several countries. Despite a generally negative reception, the film has gained notoriety as a cult classic with significant merit for its political content and historical portrayal.

A 178-minute Ultimate Cut, approved by McDowell who always felt his performance was hindered in the original version, and consisting entirely of new archival footage not used for the previous theatrical release, premiered at the Cannes Film Festival in 2023, receiving more favourable reviews from critics.

Caligula is the young heir to the throne of his great-uncle, Emperor Tiberius. One morning, a blackbird flies into his room; Caligula considers this a bad omen. Shortly afterward, one of the heads of the Praetorian Guard, Naevius Sutorius Macro, tells Caligula that Tiberius demands his immediate presence at Capri, where the Emperor lives with his close friend Nerva, Caligula's dim-witted uncle Claudius, and Caligula's cousin (Tiberius's grandson) Gemellus. Fearing assassination, Caligula is afraid to leave, but his sister and lover Drusilla persuades him to go.

At Capri, Caligula finds that Tiberius has become depraved, showing signs of advanced venereal diseases and embittered with Rome and politics. Tiberius enjoys swimming with naked youths and watching degrading sex shows that include deformed people and animals; Caligula observes with fascination and horror. Tensions rise when Tiberius tries to poison Caligula in front of Gemellus. Nerva commits suicide and Caligula tries to kill Tiberius but loses his nerve. Proving his loyalty to Caligula, Macro kills Tiberius instead with Gemellus as a witness.

After Tiberius's death and burial, Caligula is proclaimed the new Emperor, then proclaims Drusilla as his equal, to the apparent disgust of the Roman Senate. Drusilla, fearful of Macro's influence, persuades Caligula to get rid of him. Caligula sets up a mock trial in which Gemellus is intimidated into testifying that Macro murdered Tiberius, then has Macro's wife Ennia banished from Rome. After Macro is executed in a gruesome public game, Caligula appoints Tiberius's former adviser Longinus as his personal assistant while pronouncing the docile Senator Chaerea as the new head of the Praetorian Guard.

Drusilla tries to find Caligula a wife among the priestesses of the goddess Isis, the cult they secretly practice. Caligula wants to marry Drusilla, but she insists they cannot marry because she is his sister. Instead, Caligula marries Caesonia, a priestess and notorious courtesan, after she bears him an heir. Drusilla reluctantly supports their marriage. Meanwhile, despite Caligula's popularity with the masses, the Senate expresses disapproval for what initially seem to be light eccentricities. Darker aspects of Caligula's personality emerge when he brutally rapes a virgin bride and her husband on their wedding day in a minor fit of jealousy and orders Gemellus's execution to provoke a reaction from Drusilla.