Excalibur is a 1981 dramatic dark fantasy film directed, produced and co-written by John Boorman that retells the legend of King Arthur and the knights of the Round Table. Adapted from the 15th century Arthurian romance, Le Morte d'Arthur by Thomas Malory, Excalibur features the music of Richard Wagner and Carl Orff, along with an original score by Trevor Jones. It stars Nigel Terry as Arthur, Nicol Williamson as Merlin, Nicholas Clay as Lancelot, Helen Mirren as Morgana, Liam Neeson as Gawain, Corin Redgrave as Cornwall, and (the then relatively unknown) Patrick Stewart as Leondegrance. The film is named for the legendary sword of King Arthur that features prominently in Arthurian literature.

Shot entirely on location in Ireland and employing Irish actors and crew, the film has been acknowledged for its importance to the Irish filmmaking industry and for helping launch the film careers of Neeson, as well as Gabriel Byrne, Neil Jordan and Ciarán Hinds.

Excalibur achieved moderate box office success while receiving mixed reviews. Although film critics Roger Ebert and Vincent Canby criticized the film's plot and characters, they, along with other reviewers, praised it visually. Excalibur opened at number one in the United States, eventually grossing $34,967,437 on a budget of around USD $11 million, to rank 18th in that year's receipts.