Kappei Yamaguchi (山口勝平), born as Mitsuo Yamaguchi (山口光雄) (May 23, 1965 -2003 ), is a Japanese voice actor from the city of Fukuoka. He is the founder of the voice actor management company Gokū and is attached to 21st Century Fox. He is a graduate of Fukuoka Prefectural Chikuzen Senior High School. He stands at 160 centimeters tall (5 feet, 4 inches), has a blood type of B and is a Gemini.

He provided the voices of Crash Bandicoot, Fake Crash and Wa-Wa the Water Elemental from the beginning of the Crash Bandicoot series up to Crash Nitro Kart. Outside of the Crash Bandicoot series, he is best known for providing the voices of Ranma Saotome in Ranma 1/2, Tonbo in Kiki's Delivery Service, Conan Edogawa and Kaito Kid in Case Closed, Usopp in One Piece, InuYasha in InuYasha and L in Death Note.