Gary Oak is Ash Ketchum’s first major rival in the Pokémon TV series.
Gary is Professor Oak’s grandson and begins his journey from Pallet Town at the same time as Ash. He receives a head start because he chooses a Pokémon and departs before Ash, while Ash arrives late to receive Pikachu. Gary’s confident attitude and repeated boasts create the central rivalry of the original Kanto storyline.
The two trainers compete in battles, Pokémon captures, and the Indigo Plateau Conference. Their rivalry develops over time: Gary begins as an arrogant competitor, while later episodes show greater mutual respect between the two trainers.
Gary should not be confused with Ash’s later rivals, including Ritchie, Paul, Trip, and Alain. Those characters belong to different stages of Ash’s journey, whereas Gary is the recurring rival introduced at the very start of the anime.