Naoki Tamanoi is a Japanese actor, voice actor, and stage director born on October 7, 1960, in Oita Prefecture, Japan. He spent much of his childhood in Hokkaido after moving there during his elementary school years. Tamanoi is a graduate of the Engeki Shudan En Theater Research Institute, which provided the foundation for his work in both performance and direction. He is affiliated with the talent agency Production Tanc and also serves as the representative of the theater company Gekidan Goshoku-no-Hana.

Tamanoi's career in the entertainment industry began in the late 1970s, with his first credited anime role appearing in 1978. Over the decades, he has built a diverse body of work that spans television animation, animated films, video games, and foreign-language dubbing. In anime, he is known for providing the voices of authoritative and mature characters. One of his most recognized roles is the Third Raikage, A, in the long-running series Naruto Shippuden. Other notable anime credits include the Titan Industry CEO in Tiger & Bunny, the Earl of Hanbridge in Little Witch Academia, and various guest roles in long-running franchises such as Detective Conan, Lupin the Third, and Sazae-san. In the film Mobile Suit Gundam Narrative, he voiced the character Mauri, and he played Show Yotsuba in the series Dream Festival! and its sequel Dream Festival! R.

Beyond animation, Tamanoi is highly active in the field of voice-over, or "fukikae," for foreign films and television series. He is particularly known as the regular Japanese voice of actor Hugh Bonneville, most notably for his portrayal of Robert Crawley, Earl of Grantham, in the Japanese version of the television drama Downton Abbey. His dubbing work also extends to major Hollywood franchises, including the Marvel Cinematic Universe, Star Wars, and films like Aquaman and Venom. In the video game industry, he has lent his voice to titles such as Ace Combat 7: Skies Unknown as Jaeger, Kingdom Hearts III, and the Resident Evil 3 remake as Mikhail Victor.

In addition to his voice work, Tamanoi has maintained a strong presence in theater. He has performed in classic stage productions, including works of Shakespeare such as King Lear and The Merchant of Venice. As a stage director, his work has been recognized for its quality, with productions being selected for events like the Agency for Cultural Affairs Arts Festival. Tamanoi is also known for his work as a narrator in documentaries and educational programs.