Kumiko Nishihara is a Japanese voice actress and stage actress born on April 27, 1965, in Chigasaki, Kanagawa, Japan. She is affiliated with the talent agency Aoni Production. Her career began in 1984, and she has remained active in the industry for several decades.

Nishihara's path to voice acting was shaped by an early interest in musical theater, which she developed after watching a performance with her mother during elementary school. While a student at Wako University, she enrolled in voice acting classes taught by fellow voice actor Kaneta Kimotsuki. When Kimotsuki established the theater company Theater Company 21st Century Fox in 1984, Nishihara left her university studies to become a founding member. With this company, she gained extensive stage experience, including playing the lead role of Alice in Alice in Wonderland on three separate occasions. This theater background provided a strong foundation for her subsequent voice acting work. In 2004, she departed from the 21st Century Fox company and transferred her voice acting representation to Aoni Production. She later co-founded an independent theater project in 2006 and continues to be active in contemporary Japanese theatre.

Nishihara is known for her distinctive high-pitched voice, which she has noted was sometimes a source of insecurity in her youth but eventually became a defining characteristic of her professional work. Her voice has been featured in numerous anime television series, original video animations (OVAs), and video games. She is also recognized for her singing abilities, having performed theme songs and character songs for various projects, including a duet for the Sakura Wars OVA.

Throughout her extensive career, Nishihara has voiced a wide array of characters. She has had prominent and long-running roles in several major franchises. She voices the character Perona in the long-running series One Piece, appearing in the television series, the special One Piece 3D2Y: Overcoming Ace's Death! Luffy's Pledge to His Friends, and the film One Piece Stampede. For the Sakura Wars series of games, anime, and films, she provided the voice for Iris Chateaubriand. In the Sailor Moon franchise, she voiced the character Diana. She has also been a part of the Precure franchise, voicing Sharuru in DokiDoki! PreCure and its related films, and Crescendo Tone in Suite PreCure.

Her other notable anime roles include Lynn Russell in Hello! Lady Lynn, Shiori Takatsuki in Revolutionary Girl Utena, Ayase Terada in s-CRY-ed, Finn Fish in Kamikaze Kaito Jeanne, and Lucemon in Digimon Frontier. She has also appeared in long-running series such as Crayon Shin-chan and Soreike! Anpanman.

Nishihara's work also extensively covers original video animations (OVAs) and video games. Her OVA roles include characters in projects such as Burn Up!, Genocyber, and Dragon Ball: Yo! The Return of Son Goku and Friends!!, where she voiced Gure. In the video game world, she is known for her role as Renne in The Legend of Heroes: Trails in the Sky and as Ruby in the Lunar games, among many others.