A.J.'s Gym is an anime location in Pokémon: Indigo League.
A.J. owns this gym. However, this gym is not an official gym. Ash challenges A.J.’s Gym showing off his Boulder badge and Cascade badge. However, A.J. says that Ash must have got him from 'amateur Gym leaders', therefore, enraging Misty and Brock. Ash later challenges A.J. but ends up getting defeated by his Sandshrew despite him using Flying type Pokémon against his ground type Sandshrew. A.J., who was desiring a record of 100 wins and 0 losses, earned another win by defeating Ash and therefore, getting 99 wins in total.
A.J. shows Ash how he trains his Pokémon. His way of training Pokémon was effective but hard. Although, he cared a lot about his Pokémon.