Mari Okamoto is a Japanese actress and voice actress born on October 31, 1954, in Tokyo, Japan. She is also known by her birth name, Mutsumi Noda. Okamoto began her career in entertainment as a child, appearing in films from a young age before transitioning to voice acting. Her early on-screen career includes roles in several films directed by Yamada Yoji, such as the Otoko wa Tsurai yo (Tora-san) series and The Yellow Handkerchief.

Okamoto's voice acting debut occurred around 1970, with her first major role being Kikuko Ogaki in the anime series Inakappe Taishō. She became a prominent voice actress throughout the 1970s and 1980s, frequently appearing in productions by Tatsunoko Production. Her work from this era includes a wide range of roles that have become classics. She voiced Junko in Time Bokan and Ai-chan, also known as Yatterman-2, in Yatterman. In the series Hana no Ko Lunlun, she played the lead role of Lunlun Flower, and she was the voice of Ranatan in The Brave Frog (Kerokko Demetan). She also took on the role of Teresa in Star Blazers: The Comet Empire (Uchū Senkan Yamato 2).

Her film work in the anime medium was equally prolific during this period. Okamoto voiced the title role of Dorothy in the 1982 anime film The Wizard of Oz. She was Rococo in the 1980 film Fumoon and played Coda in Bremen 4: Angels in Hell. In the film A Time Slip of 10000 Years: Prime Rose, she provided the voice for the character Emiya Tachi, also known as Prime Rose. She also voiced Anne d'Autriche in the series Anime Sanjushi, a role she reprised in the related film Tekkamen o Oue - D'Artagnan Monogatari yori. Her versatility extended to family-oriented specials, where she played Haruka's Mother in both Ultra Nyan: Hoshizora Kara Maiorita Fushigi Neko and its sequel Ultra Nyan 2: Happy Daisakusen, as well as voicing the titular character in Serendipity Monogatari: Pyua-tou no Nakama-tachi. Other notable credits from this time include Aiko Morimura in Hello! Spank, Misako Nishiguchi in Twelve Sets of Eyes, Sakura in an anime adaptation of Otoko wa Tsurai yo - Torajirō Wasurenagusa, and Isshuu Tsukimi in Tentō Mushi no Uta.

Okamoto has maintained a long-standing career in the industry. Her work demonstrates recurring collaborations with studios like Tatsunoko Production and with fellow voice actors such as Kamiya Akira. In her later career, she has continued to take on roles, showing her range by voicing characters in contemporary series. Examples include Professor Lukic in Little Witch Academia and Mami Ichigaya in the BanG Dream! franchise. She is affiliated with the talent agency 81 Produce.