What is the name of the first Pokémon theatrical film?

The first Pokémon theatrical film is Pokémon: The First Movie - Mewtwo Strikes Back.

The film was released in Japan on July 18, 1998, and reached North American cinemas on November 12, 1999. Its story centers on Mewtwo, a genetically engineered Pokémon who challenges trainers after learning about its origins and questioning its purpose.

Ash, Misty, and Brock are invited to New Island by a mysterious trainer. They discover that Mewtwo has created powerful cloned Pokémon and intends to prove the superiority of clones over naturally born Pokémon. The film’s central conflict leads to a battle between original Pokémon and their clones.

The title is sometimes shortened to Pokémon: The First Movie, but “Mewtwo Strikes Back” is part of the full English title. The follow-up film, The Power of One, is commonly called Pokémon 2000 and is not the franchise’s first theatrical release.