Niantic developed Pokémon Go, the location-based mobile game released internationally in 2016.
The game was created in collaboration with The Pokémon Company and Nintendo, with Niantic providing the mobile, mapping, and augmented-reality technology. Players find Pokémon in real-world locations, visit PokéStops, and battle or capture creatures through a smartphone interface.
Pokémon Go launched first in Australia, New Zealand, and the United States on July 6, 2016. Its rollout then expanded across Europe, Japan, and other regions. The game became a global cultural event and brought location-based augmented reality to a huge mainstream audience.
Niantic had already developed Ingress, another location-based mobile game whose real-world map data and gameplay ideas helped inform Pokémon Go. The Pokémon Company owns and manages the broader Pokémon brand, but Niantic is the specific developer asked for in this question.