Yoshio Inoue is a Japanese actor and singer born on July 6, 1979, in Fukuoka City, Japan. He is primarily renowned for his extensive and acclaimed career in musical theatre, where he has been a leading figure since his debut in 2000. His voice acting work, while a smaller facet of his career, includes notable roles in major anime film productions.

Inoue's path to performance was influenced by an early love for musicals, sparked after seeing a production of Cats in fourth grade. He studied vocal music at the Tokyo University of the Arts and made his professional stage debut while still a student, being cast as Crown Prince Rudolf in the musical Elisabeth. This marked the beginning of a celebrated stage career that would earn him the nickname "Prince of Musicals". He has since originated or played leading roles in numerous iconic productions, such as the title role in Mozart!, Chris in Miss Saigon, and both Rudolf and Der Tod in Elisabeth. His work has been recognized with multiple prestigious awards, including the Kikuta Kazuo Theater Award and the Yomiuri Theater Award for Best Actor. In 2013, he also formed the musical unit StarS with fellow actors Kenji Urai and Ikusaburo Yamazaki.

Inoue's venture into anime voice acting began in 2017 with a role in the film Sword Art Online The Movie: Ordinal Scale, where he voiced the character Eiji. He later reprised this role for an appearance in the Sword Art Online television series in 2020.

He was subsequently cast in his second anime role as the villain Nine in the 2019 feature film My Hero Academia the Movie -Heroes: Rising-. In the film, Nine is a powerful original villain who attacks Nabu Island in pursuit of a specific Quirk. The character was designed specifically for the film by My Hero Academia creator Kōhei Horikoshi. Inoue's performance as the relentless and formidable antagonist brought a distinct presence to the film.