Professor Oak gives the player a choice of starter Pokémon in Pokémon Red and Blue. He is the first major Pokémon researcher encountered in the original games and lives in Pallet Town.
Oak offers Bulbasaur, Charmander, or Squirtle at the beginning of the player's adventure. The rival, later known as Blue, chooses another of the three, establishing the recurring starter-selection and rival-battle structure of the series.
Professor Oak also gives the player a Pokédex and asks them to record information about Pokémon encountered during the journey. His role combines scientific research with mentorship, making him both a story guide and a practical source of early-game equipment.
The professor is named Samuel Oak in English-language materials. He is often confused with later researchers such as Professor Elm of Johto or Professor Birch of Hoenn, but Oak is the canonical professor of the first-generation Kanto games.