Mariko Higashiuchi is a Japanese voice actress from Tokyo, born on December 23, 1989. She is affiliated with the talent agency VIMS. Her path to becoming a voice actor was unconventional, as she originally aimed to be a high school teacher and earned her national teaching license for the Japanese language. During this time, she was scouted by VIMS, which led her to change her career path. She subsequently enrolled in the Japan Narration Actors Institute to train as a voice actor and joined VIMS upon graduating.

She made her debut as a voice actor in 2012, providing voices for multiple minor characters in the long-running series Naruto Shippuden. Her first successful audition for a named role was for the character Torao Kanegami, also known as Money Kinkami, in the 2014 anime series No-Rin. Known for her androgynous voice, she frequently plays young boy characters and women with more masculine traits, a versatility that has become a hallmark of her career.

Higashiuchi has built an extensive list of credits across numerous anime series. In the Cardfight!! Vanguard franchise, she voices Shinobu Kajita, appearing in Cardfight!! Vanguard overDress and its subsequent sequels will+Dress and DivineZ. She plays the role of Annabel, the elf proprietress of the Kaburaya drugstore, in Drug Store in Another World - The Slow Life of a Cheat Pharmacist. She is also the voice of Lucy Morstan, a major character in the original anime Case File nº221: Kabukicho. In the Gundam franchise, she voiced the character Rose in Gundam Build Divers and its sequel web anime, Gundam Build Divers Re:Rise.

Other significant and recurring roles in her filmography include the younger versions of multiple characters across the JoJo's Bizarre Adventure franchise, such as young Keicho Nijimura in Diamond is Unbreakable and Giorno's mother in Golden Wind. She has also played the younger self of Hatsuharu Sōma in the Fruits Basket (2019) remake, the role of young Olga Itsuka in Mobile Suit Gundam: Iron-Blooded Orphans, and various characters in the Boruto: Naruto Next Generations series.

Higashiuchi holds several certifications, including the aforementioned high school teacher's license, a Shodan (beginner's level) rank in kendo, and a Grade Pre-2 in the English proficiency test Eiken. She is also known for her singing ability, with a vocal range of 3.3 octaves.