Where it all started — 151 Pokémon, 8 gyms, one Rhydon prototype.
Red, Blue, Yellow (and the FireRed/LeafGreen remakes) · Released 1996
Kanto is the original Pokémon region, introduced in Red & Blue in 1996. The 151 Pokémon of Gen 1 defined the franchise's visual language — Ken Sugimori's hand-drawn art style, the first-generation type chart without Dark or Steel, and the 'starter trio' formula (Grass / Fire / Water) that every generation since has followed. Every competitive Pokémon metagame, every trading card set, every mainline game traces back to this one region.
Kanto is modelled on the real Kantō region of Japan, with Pallet Town standing in for rural Tochigi and Celadon City for Shinjuku. The original games had no secondary types for most Pokémon, no Special Attack / Special Defence split, and no abilities — these systems were all added in later generations and retroactively applied to Kanto mons in remakes.
Mew was added to the Red & Blue game data by developer Shigeki Morimoto in the last week of development as an Easter egg — only possible to obtain legitimately via the Nintendo Space World tournaments until the Gen 3 remakes made it accessible in normal play.