Kimiko Koyama is a Japanese voice actress and singer born on January 27, 1979, in Tokushima City, Tokushima Prefecture, Japan. Her real name is Kimiko Furuyama, which uses different characters but shares the same pronunciation as her stage name. She stands 152 cm tall. Koyama adopted a stage name written in hiragana to avoid common misreadings of her surname's characters.

Koyama's career in the entertainment industry began after she successfully passed a voice acting audition while still in high school. She joined the production company Sun Music Production immediately after graduating. Her debut anime role was as Piroro in the 1997 series Coji-Coji. In 2002, she moved to the agency Sigma Seven, and later transferred to AIR AGENCY in 2007. Since December 2011, she has worked as a freelancer.

Her voice is frequently recognized for its cute, high-pitched, and energetic qualities, making her a popular choice for youthful, mischievous, or "loli" type characters. Among her most well-known and enduring roles is Komoe Tsukuyomi, a teacher who appears youthful, in the long-running A Certain Magical Index series, its sequel A Certain Magical Index II, A Certain Magical Index III, and the spin-off A Certain Scientific Railgun. She is also known for voicing Fūka Narutaki across various adaptations of Mahō Sensei Negima!, including the television series, OVAs, and the anime film. Another significant role is Yukari Sendō in Rosario + Vampire and Rosario + Vampire Capu2. Koyama also provided the voice for Majolica le Fay in Ōkami-san & Her Seven Companions and Carina Verritti in Blessing of the Campanella. She played the character Pepe in the Shugo Chara! series and Mao Onigawara in Ground Defense Force! Mao-chan. Earlier in her career, she voiced Uzuki Shitennō in the Happy Lesson franchise, including the original OVA, the television series, and Happy Lesson Advanced. The user also correctly identifies her role as Keroriinu in Kero Kero Keroppi: Hasunoue Town Kikiippatsu!, Marianne in the Shakugan no Shana franchise, Serika Shihōdō in Kigurumikku V3, and the title character Yu-no in Yu-No. Her filmography also includes notable roles in Best Student Council as Maachi Hisakawa and Memories Off 3.5 as Haya Nonohara.

Beyond anime, Koyama's talents extend to singing. She has released solo music, contributed numerous character songs for the series she has worked on, and was a member of the voice-acting unit Pastel, which was active from 2003 to 2004 and revived in 2016. She has also voiced characters in video games, including the title role in Yu-No. Her versatility is further demonstrated by a unique career detour. In 2009, she enrolled in the 15th class of the NSC Tokyo School for Comedians, run by Yoshimoto Kogyo, to overcome her shyness and improve her public speaking skills. For nearly two years, she worked simultaneously as a voice actress and a solo comedian under the stage name Kimikimi, a rare combination in the Japanese entertainment industry.