Koichi Yamadera (山寺 宏一 Yamadera Kōichi) is a Japanese voice actor affiliated with Across Entertainment.
|1995||Ultraman: Towards the Future||Lloyd Wilder||Japanese dub|
|2015||Gridman the Hyper Agent: boys invent great hero||Takeshi Todo|
|The・Ultraman: Jackal vs. Ultraman||Demon King Jackal|
|Other male characters|
|2017||Ultraman Orb The Movie: Let Me Borrow the Power of Bonds!||Alien Gapiya Sadis|
|Shin Ultra Fight||Narrator|
|Zoku Ultra Fight|
- Ninja Scroll - Voice of Jūbei Kibagami
- Cowboy Bebop - Voice of Spike Spiegel
- Dragon Ball Z: Battle of Gods - Voice of Beerus: The God of Destruction
- Ghost in the Shell - Voice of Togusa
- Mashin Eiyuuden Wataru - Voice of Kurama Wataribe
- Neon Genesis Evangelion - Voice of Ryoji Kaji
- Anpanman - Voice of Cheese
- Ranma ½ - Voice of Ryōga Hibiki
- Lupin III - Voice of Koichi Zenigata (replacing the late Goro Naya)
- One Piece - Voice of Donquixote Rosinante
- GinTama - Voices of Yoshida Shouyou and Utsuro
- Hunter x Hunter (2011 version) - Voice of Silva Zoldyck
- Samurai Pizza Cats - Voice of Bad Bird
- Sword Art Online - Voice of Akihiko Kayaba
- Danganronpa V3: Killing Harmony - Voices of Monokuma Kubs
- Mario Kart Arcade GP 2 - Voice of Color Commentator (JP)
- Batman Ninja - Voice of Bruce Wayne/Batman
- Super Robot Wars - Voice of Daisuke Umon/Duke Fleed (Replacing the late Kei Tomiyama)
- Shrek Franchise - Dub voice of Donkey
- Koichi Yamadera's favorite Ultra Warriors are Ultraman, Ultraseven and Ultraman Ace.
- Discounting Jackal vs. Ultraman, Sadis in Orb The Movie is his first role in the Ultraman Series since Lloyd Wilder in Ultraman Great. Because of this, he was excited to return to the franchise and be casted as Sadis. Although initially nervous about this role, the director encouraged ad-libs in his role.
- He is known for his versatile range, as protagonists, antagonists, and even to the point of voicing as a female.
- Although he did not voiced Zetton in Shin Ultraman, Yamadera posted his own impression of the monster's noises on Twitter.