Which original Pokémon game was released only in Japan and not internationally?

Pokémon Green was the original Pokémon game released only in Japan.

The first Japanese release consisted of Pokémon Red and Pokémon Green for the Game Boy on February 27, 1996. Later, Japan received an updated Pokémon Blue, whose code, artwork, and presentation became the basis for the international Pokémon Red and Blue releases.

Outside Japan, players generally encountered Red and Blue rather than the original Green version. This is why international fans sometimes assume that Blue was the direct counterpart to Japan’s Red, when the initial Japanese pairing was actually Red and Green.

Pokémon Green should also be distinguished from later games and remakes that use the word “Green” in different contexts. The original Japanese Green is a first-generation Game Boy title, not a separate international release. Its version-exclusive content helped make trading an important part of completing the original Pokédex.