Lupin III: The Castle of Cagliostro (Japanese: ルパン三世 カリオストロの城, Hepburn: Rupan Sansei Kariosutoro no Shiro) is a 1979 Japanese animated action adventure comedy film co-written and directed by Hayao Miyazaki. It is the second animated feature film based on the 1967–69 manga series Lupin III by Monkey Punch. The film was Miyazaki's feature directorial debut after having previously worked as an animator for Toei Animation and Telecom Animation Film, and directing several animated television series, including Lupin III Part I.

The Castle of Cagliostro follows gentleman thief Lupin III, who successfully robs a casino—only to find the money to be counterfeit. He heads to the tiny country of Cagliostro, the rumoured source of the bills, and attempts to save the runaway Princess Clarisse from Count Cagliostro's men; the Count plans to marry Clarisse in order to cement his power and recover the fabled ancient treasure of Cagliostro, requiring Clarisse's ancestral ring. Lupin enlists his associates, Jigen and Goemon, and sends his calling card to the Count to get Inspector Zenigata, his longtime nemesis, to the castle. After becoming trapped in the dungeon under the castle, Lupin and Zenigata form a pact to escape and foil the Count's counterfeit operation and save Clarisse from her forced marriage to the Count.

The original theatrical release in Japan occurred on 15 December 1979, distributed by Toho. In North America, it was screened at various festivals in the early 1980s, while a heavily edited and shortened version became available in the form of an arcade LaserDisc video game, Cliff Hanger (1983), combined with footage from the previous Lupin III film, The Mystery of Mamo (1978). The Castle of Cagliostro eventually made its American theatrical debut on 3 April 1991, with the home release following in October 1992. This first theatrical dub was produced by Streamline Pictures and released on home video the following year. A new dubbed version was produced by Manga Entertainment in 2000 and has had several releases.

Despite initially underperforming at the box office, The Castle of Cagliostro has garnered high praise, with critics and historians noting the film's influence on Miyazaki's later works, becoming the most popular and well-regarded entry in the entire Lupin III franchise, and has since been recognised as a cult film. However, some have disapproved of its depiction of Lupin as a gallant hero instead of his original persona as a ruthless criminal. The film has served as a major influence on animators and directors worldwide, such as Pixar director John Lasseter and several Disney films, including titles of the Disney Renaissance. The Japanese computer animated film Lupin III: The First (2019) also has a plot structure loosely modelled after The Castle of Cagliostro.