Kotarō Daigo is a Japanese actor and voice actor, born on September 1, 2000, in Tokyo, Japan. He is affiliated with the talent agency A-Light. Before entering the entertainment industry, Daigo was a member of his junior high school's soccer team but left to pursue his long-standing interest in acting. His career began in 2016 with appearances in commercials and music videos.

Daigo's early performance experience was rooted in stage productions. In 2017, he was cast in the lead role of Sakamichi Onoda in the popular stage play adaptation of Yowamushi Pedal, a role he would reprise in several subsequent installments of the series through 2018. He continued his work in stage adaptations, later taking on the role of Shōyō Hinata in a Hyper Projection stage play for Haikyu!! in 2019 and portraying Haku in a stage adaptation of Spirited Away in 2022.

His most significant voice acting role came in 2019 when he was cast as the protagonist, Hodaka Morishima, in Makoto Shinkai's acclaimed animated feature film, Weathering With You. Daigo was selected for the role from an audition process that reportedly included over two thousand applicants. This performance marked his major debut in anime voice acting and brought him widespread recognition. For this role, Kotarō Daigo was one of the recipients of the Best Rookie Actor award at the 14th Seiyu Awards in 2020.

While Weathering With You stands as his most prominent voice role to date, Daigo's career is primarily centered on live-action television and film, as well as stage acting. He has appeared in numerous television dramas, including the NHK asadora Maiagare! in 2022 and an adaptation of the manga Ciguatera in 2023. His film credits include roles in live-action movies such as Re/Member (2022) and OUT (2023). His body of work demonstrates a career that spans multiple performance disciplines, with a notable achievement in voice acting for a major animated film.