Mikoi Sasaki is a Japanese voice actress and singer born on March 30, 1991, in Iwate Prefecture, Japan. She is affiliated with the talent agency Hibiki. Her career began in 2010 after she was selected from thousands of applicants to voice her debut and signature role, Hercule Barton, in the multimedia franchise Tantei Opera Milky Holmes. This role launched her career and led to her becoming a member of the voice actress singer group Milky Holmes, formed with her three co-stars.

Following her debut, Sasaki established a diverse career in anime television. Her filmography includes a wide range of supporting and lead roles. She voiced the title character in Shiba Inuko-san, Kuguru Uki in the Future Card Buddyfight series, and Himeno Katsuragi in Da Capo III. She also played Neko in Recently, My Sister Is Unusual, Piyo-tan in Etotama, and Kumi Okazaki in Cardfight!! Vanguard G. In 2017, she joined the cast of the hit series Kemono Friends as Royal Penguin, a role she reprised for the second season and a subsequent stage play adaptation. She continued to take on varied roles, appearing as Fumi in the Hulaing Babies shorts, Shizuha Kochou in the Shōjo☆Kageki Revue Starlight game and its related media, and as Gobco Ngière in Peter Grill and the Philosopher's Time and its sequel Super Extra. More recently, her credits include Yuzu Hosono in Teppen—!!!!!!!!!!!!!!!, Kawaii ne Onee-san in YouTuNya, and a young Tsubaki Aoyagi in D4DJ Double Mix.

In addition to anime, Sasaki has been active in other areas of voice acting. She has voiced characters in numerous video games, such as Kururu in The Great Cleric and Shizuha Kochō in Revue Starlight -Re LIVE-. Her work extends to dubbing foreign content, including the role of Rarity in the Japanese dub of My Little Pony: Friendship Is Magic. She has also performed in stage adaptations, including the Kemono Friends stage play and Devil May Cry: The Live Hacker. Outside of performance, Sasaki has been a regular personality on various radio programs, often related to the series she stars in, and she hosts a YouTube channel with fellow voice actresses Aimi and Ayasa Ito.