In which Pokémon region is Pokémon Pokopia set?

Pokémon Pokopia is set in a post-apocalyptic version of the Kanto region.

The game reimagines Kanto as a landscape abandoned by humans and unsuitable for Pokémon. Rather than visiting familiar cities for battles and badges, players help rebuild habitats and make the damaged environment livable again.

The story begins when Ditto discovers a world where humans have departed. Ditto then meets Professor Tangrowth and helps investigate what happened while restoring areas needed by Pokémon. This gives the familiar region a very different tone from the original Pokémon games, where Kanto is a populated setting centered on trainers and Gyms.

Johto, Sinnoh, and Paldea are other official Pokémon regions, but they are not the answer for Pokopia's setting. The game also includes Pokémon from Generations I through IX, so the presence of later species does not change the region in which the story takes place.