Which studio developed Pokémon GO?

Niantic developed Pokémon GO.

Niantic created Pokémon GO as a location-based augmented-reality mobile game in partnership with Nintendo and The Pokémon Company. The game uses GPS to determine a player’s location and places virtual Pokémon, PokéStops, and Gyms around the real world.

The project built on ideas from Niantic’s earlier game Ingress, which also encouraged players to visit real-world locations. Pokémon GO adapted that exploration model for a much broader audience by combining it with Pokémon collecting and battling.

Game Freak developed the main Pokémon role-playing games, so it is a common but incorrect answer for Pokémon GO. Nintendo and The Pokémon Company were major partners and publishers, but Niantic was the studio responsible for developing the mobile game.