The original Pokémon Red and Green games are set in the fictional region of Kanto.
Kanto contains the towns, routes, caves, seas, and eight Pokémon Gyms that players explore during the first-generation adventure. The player’s goal includes defeating Gym Leaders, challenging the Pokémon League, and completing the Pokédex.
Although the setting is called Kanto in later descriptions, the region’s name was not used in the original first-generation games. It became explicitly identified with the release of the second generation, Pokémon Gold and Silver.
Kanto is inspired partly by the real Kantō region of Japan, which includes Tokyo and surrounding areas. The game’s fictional geography is not a direct map, but the shared name helps explain several cultural and geographic influences in the setting.