Excalibur is a 1981 epic medieval fantasy film directed, co-written and produced by John Boorman, that retells the legend of King Arthur and the knights of the Round Table, based loosely on the 15th-century Arthurian romance Le Morte d'Arthur by Thomas Malory. It stars Nigel Terry as Arthur, Nicol Williamson as Merlin, Nicholas Clay as Lancelot, Cherie Lunghi as Guenevere, Helen Mirren as Morgana, Liam Neeson as Gawain, Gabriel Byrne as Uther and Patrick Stewart as Leondegrance. The film is named after the legendary sword of King Arthur that features prominently in Arthurian literature. The film's soundtrack features the music of Richard Wagner and Carl Orff, along with an original score by Trevor Jones.

Boorman's Excalibur began development as an unproduced adaptation of The Lord of the Rings. The film was shot entirely on location in Ireland and at Ardmore Studios, employing Irish actors and crew. It has been acknowledged for its importance to the Irish filmmaking industry and for helping launch the film and acting careers of a number of Irish and British actors, including Liam Neeson, Patrick Stewart, Gabriel Byrne and Ciarán Hinds.Film critics Roger Ebert and Vincent Canby criticised the film's plot and characters, although they and other reviewers praised its visual style. Excalibur opened at number one in the United States, eventually grossing $34,967,437 on a budget of around US$11 million to rank 18th in that year's receipts. It won the award for Best Artistic Contribution at the 1981 Cannes Film Festival, and received an Oscar nomination for Best Cinematography and a BAFTA nomination for Best Costume Design.