Uko Tachibana is a veteran Japanese voice actress born on March 15, 1973, in Tokyo, Japan. She is affiliated with the talent agency Kenyu Office and was formerly known by the stage name Mari Koshi. Her path to voice acting was shaped by an early passion for sports; she developed her distinctive, husky voice from cheering loudly as a member of her school's softball club. After a knee injury ended her aspirations of becoming a national-level athlete, she pursued voice acting on the suggestion of a classmate. She trained at the Katsuta Voice Actor Academy and gained foundational experience as a member of the theater group 21st Century FOX for approximately ten years.

Tachibana is known for her versatile and recognizable husky tone, which allows her to portray a wide range of characters, from young boys and tough personalities to elderly women and quirky individuals. Her career spans numerous major anime series. She has had recurring roles in long-running franchises such as One Piece, where she voiced Miss Doublefinger and Charlotte Praline, and in Detective Conan, Crayon Shin-chan, Doraemon, and Ojamajo Doremi. In the 2017 film Genbanojō, she provided the voice for the character Jirō. In the 2018 short anime Engimon, she voiced Kin-chan, a goldfish paper balloon character. That same year, she voiced the role of Mrs. Hidoro, the powerful wife of the Hidoro family patriarch, in an original video animation (OVA) episode of Golden Kamuy.

Beyond anime, Tachibana has an extensive presence in video game dubbing. She is notably the Japanese voice of Mad Moxxi in the Borderlands series and Mad Maggie in Apex Legends. Her work also includes voice roles in international series dubs, such as Dr. T'Ana in Star Trek: Lower Decks. In addition to her performance work, she shares her expertise as a lecturer at the Tokyo Anime & Voice Acting College, mentoring aspiring voice actors. Her enduring presence and consistent demand across a wide variety of roles in anime, video games, and dubbing mark a significant and accomplished career in the Japanese voice acting industry.