Tomoko Miyadera is a Japanese actress and voice actress affiliated with the theater company Gekidan Seinenza. She was born on October 4, 1956, in Kumamoto Prefecture. She is a graduate of Musashino Academia Musicae. Following her graduation from the Seinenza Research Institute, she joined the theater company in April 1982, beginning a career that has spanned over four decades.

Her career is built on a strong foundation in stage performance with Gekidan Seinenza, where she has appeared in numerous productions. This is complemented by an extensive body of work in voice acting, particularly in the dubbing of foreign films and television series. Her voice is featured in Japanese-language versions of a wide range of international films and shows, often providing voices for actresses such as Glenn Close, Marcia Gay Harden, and Catherine O'Hara. Notable dubbing roles include Margo Channing in All About Eve, Maggie Seaver in Growing Pains, and Miranda Priestly in The Devil Wears Prada.

In anime, Miyadera is recognized for several long-running and prominent roles. She voices Masae Ohyama, the mother of the main character, in the long-running series Crayon Shin-chan. She also voices the character Suzu (also known as Hachigetsu) in Naruto. Other television anime credits include roles in Ninja Sentai Kakuranger as Hieda no Kihachi, Detective Conan as Yumi Horikoshi, Maria Watches Over Us as Seiko Kasuga, and Major as the orphanage director.

In the original Netflix anime series Hero Mask, she provides the voice for the character Anna Winehouse. She is also part of the cast for the short film Sugar Sugar Rune Les deux sorcières, a 3DCG prequel to the Sugar Sugar Rune story, where she voices the character Cauldron.

Her work also extends to video games and other media. Notably, she voices the character Marle in the Japanese version of the role-playing game Final Fantasy VII Remake. Her career includes performances in radio dramas, television dramas, and commercials. She has also appeared in live-action television dramas such as Katekon and The Veteran Detective.