Pokémon Red and Blue are set in the fictional region of Kanto.
Kanto contains the towns, routes, caves, islands, and Pokémon Gyms that the player explores while pursuing the Pokémon League title. Important locations include Pallet Town, Viridian City, Pewter City, Cerulean City, Saffron City, Cinnabar Island, and the Indigo Plateau.
The region is inspired by Japan’s real Kantō region, but the Pokémon setting is a fictional interpretation rather than a direct recreation. In the original Japanese games, the name Kanto was not used until the second generation, even though later games and reference materials identify the first-generation setting by that name.
Kanto is sometimes confused with Johto because Pokémon Gold and Silver allow players to visit both regions. Johto is the main setting of the second-generation games, while Kanto is the original region from Red, Green, Blue, and Yellow.