Gyms (ジム, Gym) are buildings located throughout various regions in the Pokémon Universe, run by its top member, a Gym Leader. Pokémon Gyms serve a couple of different purposes, one is to help in the training of a Trainer's Pokémon. These members strengthen their Pokémon inside the Gym with the help of the Gym Leader, and will challenge anyone looking to battle the Gym Leader.
The second purpose is to test the skills of traveling Trainers looking to enter into the regional League. In order to test their skills, a Gym Leader will engage in a Pokémon battle with the Trainer. Should the challenger win, they will receive a badge which shows that they have defeated that Gym Leader along with a TM of the type depending on the gym.
Gyms usually specialize in a certain type of Pokémon, meaning that all members carry a team of Pokémon with one common type. Additionally, most Gyms contain puzzles which a trainer must bypass in order to reach the Gym Leader. This is more a common factor in the Game series rather than the Pokémon Anime series.
- There could be more than eight gyms in each region in the anime due to the fact that Gary and other characters have shown their badge cases to Ash, usually having a few different badges than he has.
- The existence of alternative gyms can also be proved by the fact that characters say that there is "a" gym in a town, not "the" next gym, even when there is one badge left to earn, where he would say that "the" next gym was there if there were not, and by the fact that Roxie, the gym leader of Virbank City, acted as the final Unova gym leader for Ash as opposed to Drayden.
- In the Generation VII Alola games, gyms were replaced with The Rite of the Island Challenge.