Mari Shimizu is a pioneering Japanese voice actress, born on June 7, 1936, in Urawa, Saitama, Japan. She is affiliated with the talent agency 81 Produce and is widely recognized as one of the foundational figures in the anime industry, often referred to by the nickname Mother of Voice Actors.

Shimizu's path to voice acting began on the stage. The daughter of actor Gen Shimizu, she was cast as the titular character in her father's theater troupe production of The Adventures of Pinocchio when no child actor was available, an experience that inspired her to pursue acting. She later trained at the Haiyuza Theatre Company's school.

Her career became forever linked with manga artist Osamu Tezuka. In 1962, Tezuka was introduced to Shimizu after an acquaintance noted the connection between Pinocchio and Tezuka's character Astro Boy. Although she was unfamiliar with manga at the time, she was cast as the voice of the titular robot boy in the 1963 Astro Boy television series. This role made her the first voice of a character who would become a cultural icon. She reprised the role for the 1980 color remake of Astro Boy and the 2000 film The Last Mystery of the 20th Century, finally retiring from the part in 2003.

Throughout her long career, Shimizu has voiced a wide array of characters, frequently in productions based on the works of Osamu Tezuka. Her filmography includes a significant number of roles from the 1960s through the 1980s. Among her most notable performances are Bero in Yōkai Ningen Bem (1968), the titular character in Jetter Mars (1977), and Jim Hawkins in the 1978 adaptation of Treasure Island. She also voiced Prince Alor in Beast King GoLion (1981). In addition to the roles of Atom, her work in Tezuka adaptations includes Adam Nasenkopf in Undersea Super Train: Marine Express (1979), Astro Boy: Shinsen-gumi, and Astro Boy: Hero of Space, as well as a role in the 2004 Black Jack series.

Shimizu's contributions to anime have been recognized with numerous industry awards. She received a Special Achievement Award at the 5th Tokyo International Anime Fair in 2006, the Synergy Award at the 3rd Seiyu Awards in 2009, and a Merit Award at the 11th Seiyu Awards in 2017. Beyond her performing career, she has also worked as a voice acting teacher and published her autobiography, Living With Astro Boy: The Anime World As Told By A Voice Actor, in 2015.