Koutaro Nishiyama is a Japanese voice actor and singer from Kanagawa Prefecture, Japan. He is currently affiliated with 81 Produce. His major roles are Atsushi Kinugawa in Cute High Earth Defense Club Love!, Sakutaro Kirara in Jewelpet: Magical Change, Kazunori Uesugi in Tantei Team KZ Jiken Note, Yoshiharu Hisomu in Kiznaiver and Ryūichi Kashima in School Babysitters. In 2018, he won the Best New Actor Award at the 12th Seiyu Awards.