X, also known as X/1999 and X: The Movie, is a 1996 Japanese animated film directed by Rintaro and animated by Madhouse. Rintaro wrote it alongside Clamp head writer Nanase Ohkawa. It is based on Clamp's manga series of the same name. It premiered on August 3, 1996, in Japan and had a limited screening in North America during 2000. The film focuses on the roles Kamui Shiro, Kotori Monou, and Fuma Monou play in the Apocalypse. After his mother's death, the young Kamui returns to Tokyo to participate in a Holy War between two groups that will either protect mankind or protect nature at the cost of mankind.

Rintaro was approached by Kadokawa Shoten to direct this movie and found this part of his career unique due to how he worked with Ohkawa, Clamp's head writer, while also aiming to show a self-contained story with a style and atmosphere that might be accepted by the viewers. The film's theme song is "Forever Love" by X Japan. The film was released in both VHS and DVD format.

Critical response to the film was generally positive with critics praising the story, visuals and fight choreography; the relationship between Kamui and Fuma was also met with positive response. Furthermore, books focused on films praised Rintaro's film while the anime television series produced years later by Madhouse was felt superior due to the further handling of the cast.