Mariko Onodera is a former Japanese voice actor from Osaka Prefecture, born on February 22, 1973. Her interest in voice acting began during her middle school years after learning about the profession, though she did not initially consider it as a personal career path. Inspired by a friend's suggestion, she enrolled in the ninth class of the Aoni Juku Osaka branch, the training school for the talent agency Aoni Production, to which she would later belong. Her professional career as a voice actor was brief, spanning from 1993 to 1995.

Despite her short time in the industry, Onodera was active during the tail end of the third voice acting boom and was regarded as a promising newcomer, appearing in several voice acting magazines. This promise was highlighted when she was a guest on the radio program Seishun Radimenia. The host, Kazuo Iwasaki, commented that he felt the wind from her, a remark he had previously made about a young Megumi Hayashibara, hinting at a potential future as a leading figure in the voice acting world.

Onodera took on a variety of roles across television, film, and original video animation. Her television anime credits included minor roles in series such as Seven Seas, Muka Muka, Marmalade Boy, and the title character Princess Piripatta in the Anime Sekai no Dowa segment. She also had roles in the popular Sailor Moon franchise, appearing as a bloodmobile announcer in the Sailor Moon S TV series and as a snow dancer in the associated film, Sailor Moon S: The Movie - Hearts in Ice. One of her notable OVA roles was as Hisami Aoike, also listed as Kumi Aoike, in the 1994 series Sei Mikaela Gakuin Hyōryūki II, known in English as Sins of the Sisters. Other OVA appearances included roles in 3×3 Eyes, Minky Momo, and as Mei Star in Private eye dol.

Onodera's voice was also featured in several video games. She is perhaps best known for her role as Tanaka Mika in the PC Engine version of the classic game Dōkyūsei. She also contributed to the soundtracks of some of her projects, performing the theme song for the Private eye dol OVA. In 1995, she released a solo album titled Person.

In 1995, at the peak of her initial success as roles, particularly in games, were increasing, Mariko Onodera chose to retire from voice acting. The specific reasons for her retirement are not publicly detailed, though reports from the time suggest it was related to her parents' initial opposition to her career choice. Early interviews indicated her family had only agreed to support her pursuit of voice acting for a limited period of two years. Her final performance was in the OVA series Minky Momo, after which she ended her career.