Professor Oak is Ash Ketchum's professor and an old friend of Mr. Miyagi. He is also the grandfather of Gary Oak. He made his first appearance in Kids World's Adventures of Pokémon: The Movie 2000.
- He is voiced by Tara Jayne (as a child in Pokemon 4Ever), Stan Hart (1998-2006), and Jimmy Zoppi (2006-present).
- Professor Oak made his first and only young appearance as Sammy Oak in Kids World's Adventures Series.