Keiko Watanabe is a Japanese voice actress and singer born on March 29, 1987, in Saitama Prefecture. She began her career after training at the Japan Narration Actor Institute, making her debut in 2008 with minor roles in series such as True Tears and xxxHolic. For many years, she voiced a variety of supporting characters in anime like Darker than Black: Gemini of the Meteor and JoJo's Bizarre Adventure, building a strong foundation in the industry.

Watanabe is known for several major and recurring roles that have defined her career. She is the voice of Momoko Suou in The Idolmaster Million Live! franchise, a role she has played since the character's introduction in the 2013 video game and reprised for the 2023 anime adaptation. In the Uma Musume Pretty Derby franchise, she voices the race horse girl Narita Taishin, a role she originated in the 2018 original video animation BNW no Chikai. Her other prominent anime roles include Minami Ōyaba in Urawa no Usagi-chan, Rea Katagiri in World's End Harem, Anna in The Faraway Paladin, and Erica in Chillin' in My 30s After Getting Fired from the Demon King's Army.

In addition to her anime work, Watanabe has an extensive career in video games and has performed numerous character songs, particularly for The Idolmaster and Uma Musume franchises. On March 29, 2022, she released her first solo song, titled Alive. As of November 30, 2019, Watanabe became a freelancer after previously being affiliated with the talent agency Crazy Box.