Which Pokémon film was the first feature-length animated movie in the franchise?

Pokémon: The First Movie was the first feature-length animated movie in the Pokémon franchise.

The Japanese film premiered on July 18, 1998, under a title translated as Pocket Monsters the Movie: Mewtwo Strikes Back. It was directed by Kunihiko Yuyama and centers on Mewtwo, a powerful Pokémon created through genetic experimentation. The story brings Ash and his friends into conflict with Mewtwo and its plan to challenge the original Pokémon.

International releases used the title Pokémon: The First Movie, with the subtitle Mewtwo Strikes Back prominently associated with it. The English-language version reached North America in November 1999, more than a year after the Japanese theatrical release.

The film is often confused with Pokémon the Movie 2000, whose Japanese title concerns Lugia. The first movie also included the short Pikachu's Vacation in many theatrical presentations. In 2019, it received a computer-animated remake called Pokémon: Mewtwo Strikes Back—Evolution.