Pokémon: The First Movie was originally released in Japan in 1998.
The film, later marketed internationally as Pokémon: The First Movie—Mewtwo Strikes Back, premiered theatrically in Japan on July 18, 1998. It centers on Mewtwo, a genetically engineered Pokémon who challenges the role of humans and Pokémon in the world.
The Japanese theatrical release came during the franchise's rapid expansion beyond video games. The movie was accompanied by the short film Pikachu's Vacation, which helped make the theatrical event feel like a major Pokémon celebration for younger audiences.
The international release dates were later. It opened in the United States in November 1999 after distribution arrangements involving Warner Bros. and 4Kids Entertainment. Confusing the Japanese premiere with the North American release is the main reason both 1998 and 1999 appear in discussions of the film.