Kōichi Yamadera (山寺 宏一, Yamadera Kōichi) is a Japanese voice actor.
He is known for his roles in Cowboy Bebop (as Spike Spiegel), the Yakuza videogame series (as Shun Akiyama). Ghost in the Shell (as Togusa), Neon Genesis Evangelion (as Ryoji Kaji), Gintama (as Shoyo Yoshida / Utsuro), Dragon Ball Super (as Beerus) and Lupin III (as the official voice of Koichi Zenigata since 2011). For Disney, he is the official dubbed voice of Donald Duck, Genie and Stitch (among others) in Japanese.
In the live action field, he is the official dub-over artist of Will Smith (Yamadera met Smith several times), Eddie Murphy and Jim Carrey. He is also known for voicing Chris Tucker, Jean-Claude Van Damme, Robin Williams, Mike Myers, Stephen Chow, Brad Pitt, Charlie Sheen, Michael Keaton, Michael J. Fox, Will Ferrell, Chris Pratt and Jon Hamm in the Japanese language releases of their respective films.
From 1993 to 2006, he was married to fellow voice actress Mika Kanai.