Pokémon Red and Blue primarily take place in the fictional region of Kanto.
Players travel through Kanto while collecting Pokémon, challenging eight Gym Leaders, and progressing toward the Pokémon League. The region includes locations such as Pallet Town, Viridian City, Lavender Town, Celadon City, and the Indigo Plateau.
Although the original games clearly use the Kanto setting, the name Kanto was not used in the first-generation games themselves. The region was named explicitly in later Pokémon titles, especially Pokémon Gold and Silver, which allowed players to revisit it.
Kanto is based broadly on the real Kantō region of Japan. Its geography and settlement names helped establish the regional structure that became a defining feature of later Pokémon games.