Kōichi Yamadera (山寺 宏一 Yamadera Kōichi?, born June 17, 1961, Shiogama, Miyagi Prefecture, Japan) is a Japanese voice actor, actor, tarento, narrator, master of ceremonies and impressionist 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.
His nickname is Yama-chan (山ちゃん Yama-chan?). As a radio personality, he is known as Bazooka Yamadera (バズーカ山寺 Bazūka Yamadera?) among other things. He is best known for his roles in Ninja Scroll (as Jūbei Kibagami), Cowboy Bebop (as Spike Spiegel), Dragon Ball Z: Battle of Gods (as Beerus), Ghost in the Shell (as Togusa), Neon Genesis Evangelion (as Ryoji Kaji), Anpanman (as Cheese), Ranma ½ (as Ryōga Hibiki/P-chan and the Jusenkyō Guide) and the current voice of Koichi Zenigata (Lupin III). He is known for voicing Jim Carrey and Eddie Murphy in the Japanese language releases of their respective films.