Ranko Mizuki was a Japanese voice actor and actress born on April 24, 1929, in Tokyo, and she passed away on May 26, 1997. Her real name was Mitsuyo Miyata. She began her career in the entertainment industry after joining the Gekidan Bunka-za theatrical troupe while still in high school. She subsequently was a member of the Gekidan Suiyokai before co-founding the theatre company Gekidan Ashi. Throughout her career, she balanced work as a stage actress with voice acting in anime and dubbing foreign films.

Mizuki is known for several significant roles in anime television series and films. She provided the voice for Boobo in the 1975 anime series Gamba no Bouken (The Adventures of Gamba). She later reprised the role of Boobo for the 1991 series Gamba to Kawausu no Bouken (The Adventure of Gamba and Otters). In the 1986 anthology series Seishun Anime Zenshu, she voiced a character named Shizu. Her other prominent anime roles include Martha obasan (Aunt Martha) in the 1987 series Ai no Wakakusa Monogatari (Tales of Little Women) and Noriko in the 1988 series Hai Akko Desu. She also voiced Anita Radcliffe in the anime adaptation of 101 Dalmatians.

In addition to her work in anime, Mizuki was highly active in dubbing foreign films and television series. She was particularly renowned as the regular Japanese dubbing voice for the actress Ingrid Bergman, providing the voice for her roles in classic films such as Casablanca and Anastasia.