OLM produced the Pokémon television series.
OLM, Inc. is a Japanese animation studio known internationally for its work on Pokémon. The studio handled the animated television production that brought Ash, Pikachu, and the Kanto region from the games to television.
The Pokémon anime was not simply a direct recording of game events. OLM and the production team built character-driven episodes around Ash's travels, Gym challenges, friendships, and recurring encounters with Team Rocket. That adaptation helped the franchise reach viewers who had never owned a Game Boy.
Toei Animation and Studio Ghibli are also major Japanese animation names, but neither produced the main Pokémon television series. The franchise's animated films and special projects have involved additional production partners over time, which is why OLM is the most specific answer for the long-running television production.