Max (Japanese: マサトMasato) is the younger brother of May in the anime. He has not yet received a Pokémon because he is under-age, but he became one of Ash's companions and joined Ash, Brock and his sister in order to see new Pokémon.
Max is a genius in the theory of Pokémon training, but he was too young to receive a Pokémon when he first appeared. Both May and Max are the children of Norman, the Gym Leader of Petalburg City and his wife Caroline. The two have a very close relationship. They often get upset with each other, but when they are in dangerous situations they try to protect each other, especially May. She sometimes gets angry with Max because he knows a lot about Pokémon and she is annoyed by not knowing the basics of training or Pokémon. He decided to travel with Ash and May to see even more Pokémon.
When Ash arrived at the gym without May in Petalburg City, he was met by little Max who was surprised to meet a trainer who he had watched on television only weeks ago, through participation in the Johto League Silver Conference. But he also mocked him for losing in the quarter finals of the tournament. He also criticized the Pokémon May chose, Torchic, saying he would have chosen a Treecko.
During his travels with his sister and his friends, Max was in charge of May's PokéNav, acting as a guide. Later on in the series, Max makes a habit of pulling Brock's ear when he sees and talks to a pretty girl, halting his romantic advances as Misty did in Kanto and Johto and the way Croagunk would Poison Jab Brock in Sinnoh for similar effect.
Max befriended a Poochyena and, although his three brothers were born at the same time, Poochyena was unable to evolve like them. The only move he knew was Tackle so Max started teaching him to use Bite. After a battle with Team Rocket, where he used that move to break through his bindings, he finally evolved into Mightyena.
While Max was walking around in a building with Ash, May and Brock, he accidentally stepped on Poliwag's tail and it immediately came out. After Max apologized to the Tadpole Pokémon, it was revealed that it belonged to the Pokémon Trainer's School in Hoenn. Later on, Max was given Poliwag as he was choosing a Poké Ball for the training arena. It was narrowly defeated by Tommy's Magby as Team Rocket interrupted the match as they were stealing Poké Balls from the Deposit Room. While Poliwag distracted Team Rocket, Magby's Flamethrower burned the Wurmple mecha Team Rocket was on and they were blasted off.