From Bulbapedia, the community-driven Pokémon encyclopedia.
Unshō Ishizuka (Japanese: 石塚運昇 born May 16, 1951) is a Japanese voice actor for the Pokémon anime. His most notable roles are that of Professor Oak and the unseen narrator.
Ishizuka is best known for his deeper voices, and is generally typecast as older, more mature male characters. Aside from his main roles, he is not officially credited for most of his roles in the ending credits.
Famous non-Pokémon roles
Note: In the case of dubbing roles, the name of the character and TV show/movie/franchise are followed by the original English actor's name in parentheses.