Ryōtarō Yamaguchi is a Japanese voice actor affiliated with Sony Music Artists. He was born on June 13, 1998, in Matsue, Shimane Prefecture, Japan, and stands 178 cm tall. His path to a voice-acting career began in October 2015 when he was selected as a finalist in the 4th Anistoteles voice actor audition, which was sponsored by his current agency.

Yamaguchi's early career included roles in video games before landing significant parts in anime television series. In 2022, he was cast as Tsubaki Yukinaga, a main character, in the mixed-media project Futsal Boys!!!!!. He voiced the role in both the television anime and the game Futsal Boys!!!!! High-Five League. A significant milestone in his career came in 2023 when he was cast as Banri Naoe, another main character, in the television anime series UniteUp!. He reprised this role for the second season, UniteUp! -Uni:Birth-, which aired in 2025.

In addition to these prominent roles, his anime credits include a minor role as a demonstrator in the series Tokyo 24th Ward in 2022. His work in video games extends to earlier titles such as the 2018 game Gakuen Shimotsuki: Anata wa Watashi no Unmei no Shimotsuki, where he played Tsubaki Takumi, and WAR OF BRAINS Re:Boot, where he voiced the characters Jax and Weather Report.

Beyond animation and games, Yamaguchi has participated in stage readings and live performances. His stage credits include the 2017 play Sayonara nante Ienai yo, the 2019 reading drama Shurin-dō Yakumo 2019 held in his hometown of Matsue, and Act Session Vol.1 Kishō Tenketsu in 2022. He has also been a regular performer on the Tokyo MX program Seigi no Eiyū in 2021. As part of his voice acting work, he has contributed character songs for his roles, including music for Futsal Boys!!!!! and as his UniteUp! character EVAN, later as part of the unit PROTOSTAR within the project. Notably, he holds the official qualification of a Pokemon Card Game Judge.