Kōichi Yamadera (山寺 宏一, Yamadera Kōichi; Miyagi, 17 de Junho de 1961) é um ator Japonês e Seiyū.
Agatha Christie no Meitantei Poirot to Marple (Norman Gale (episodes 36-39))
Ah! My Goddess: Everyone Has Wings (Troubador (episode 12))
Alexander Senki (Darius III of Persia)
Allison & Lillia (Carr Benedict)
Ashita Free Kick (Ūgo (episode 29))
Astro Boy (2003 TV series) (Memata (episode 21))
Brave Exkaiser (Osamu Tokuda, trader, Narrator)
Brave Police J-Decker (Miruamiigo, Uno, Osōjioba-san, giant)
Char's Counterattack (Gyunei Guss)
City Hunter (Abe, hitman, skunk, Inspector Fukamachi, additional voices)
City Hunter 2 (Silver fox, announcer, Rubāto, Shirozaru, hitman, government person, Mosada, Misawa, Megane, Akira, Kazama, Master, old person, Schmit, additional voices)
City Hunter: Goodbye, My Sweetheart (Professor Takeaki Mutō)
Dā! Dā! Dā! (Yuzuhiko (episode 51))
Detective Conan (Kyōsuke Haga (episodes 385-387), Masateru Hira (episode 449))
Digimon Xros Wars (Ballistamon)
Dokkiri Doctor (Doctor Haruka Nishikikōji, narrator)
Dragon Ball Z (Tenshinhan (episodes 82 and 84))