Koichi Yamadera (山寺 宏一, Yamadera Kōichi, born June 17, 1961) is a Japanese actor, voice actor, narrator and singer from Shiogama, Miyagi Prefecture. He graduated from Tohoku Gakuin University's economics school and is currently affiliated with Across Entertainment. Before that, he was affiliated with the Tokyo Actor's Consumer's Cooperative Society.He is known for his roles in Gintama (as Utsuro), Cowboy Bebop (as Spike Spiegel), the Yakuza videogame series (as Shun Akiyama), Shōwa Genroku Rakugo Shinjū (as Sukeroku), Ghost in the Shell (as Togusa), Neon Genesis Evangelion (as Ryoji Kaji), Ninja Scroll (as Jūbei Kibagami), Dragon Ball Super (as Beerus), Anpanman (as Cheese), Ranma ½ (as Ryōga Hibiki/P-chan and the Jusenkyō Guide), Space Battleship Yamato 2199 (as Aberdt Desler) and the second generation voice of Koichi Zenigata (Lupin III). In the live action field, he is the official dub-over artist of Will Smith (Yamadera met Smith several times) and Jim Carrey. He is also known for voicing Eddie Murphy, Stephen Chow, Robin Williams, Chris Tucker, Jean-Claude Van Damme, Brad Pitt, Charlie Sheen, Michael J. Fox, Michael Keaton, Will Ferrell, Jon Hamm and Mike Myers in the Japanese language releases of their respective films. For Disney, he is the official dubbed voice of Donald Duck and Stitch (among others) in Japanese. He also voiced Batman in the Japanese version of the film Batman Ninja. He's also been in every Pokémon film to date.
Yamadera married fellow voice actress Mika Kanai on May 23, 1993. They divorced in 2006, although it wasn't publicized until 2007. He then married Japanese voice actress Rie Tanaka on June 17, 2012, with a ceremony held in Hawaii on January 3, 2013. In August 2018, they announced that they had filed for divorce. On June 14, 2021, his marriage to radio personality Robin Shoko Okada was announced.