Which company developed Pokémon Red and Green for the Game Boy?

Game Freak developed Pokémon Red and Green for the Game Boy.

Game Freak was founded by Satoshi Tajiri and became the main development studio behind the Pokémon video-game series. Nintendo published the games and handled their release, but publishing and development were separate roles.

The original games were designed as role-playing games in which players explored a region, captured Pokémon, trained them, and battled other Trainers. Game Freak's work established the core structure that later main-series games continued to use, including exploration, turn-based battles, evolution, and version-exclusive Pokémon.

Creatures is another company frequently associated with Pokémon, particularly because it helped develop later games and manages important franchise businesses, including the Pokémon Trading Card Game. Nintendo is also central to the franchise as publisher and platform owner. Neither company, however, is the developer credited for the original Game Boy titles; that credit belongs to Game Freak.