Kanto is the original fictional region featured in Pokémon Red, Green, Blue, and Yellow.
The player begins the adventure in Pallet Town and travels through Kanto to challenge eight Gym Leaders before facing the Elite Four and the Pokémon Champion. Professor Oak gives the player the first Pokédex and introduces the region's Pokémon research mission.
Kanto is also the setting of the first Pokémon anime series and many later games connected to the original storyline. Its name is shared with the real-world Kantō region of Japan, although the Pokémon region is a fictionalized setting.
Johto, Hoenn, and Sinnoh are regions introduced in later generations. Johto is especially connected to Kanto because Pokémon Gold and Silver allow players to revisit Kanto after completing the Johto portion.