Sanae Kobayashi is a Japanese voice actress born on January 26, 1980, in Hamamatsu, Shizuoka Prefecture. Initially aspiring to be an actress, she was a member of a local musical theater group during high school. Her talent was noticed by veteran voice actor Kazuya Tatekabe during a performance in Tokyo, which led to her being scouted for the voice acting industry. She made her debut in 2000 and was formerly affiliated with Production Baobab before moving to Sigma Seven in 2015.

Kobayashi is widely recognized for her exceptionally broad vocal range, often described as one of the few voice actors with a "seven-colored voice". This versatility allows her to portray a vast array of characters, from young boys and teenage girls to mature, cool-headed women, as well as characters with split personalities. This skill is evident in some of her most celebrated early lead roles, including the quiet and intense Akira Toya in Hikaru no Go, the dual roles of the innocent Nyu and the violent Lucy in Elfen Lied, and the title character in Madlax. She also provided the voice for Allen Walker in the 2006 series D.Gray-man.

Throughout the 2000s, Kobayashi amassed an extensive list of credits in major anime series. She played Maya Kitajima in the 2005 adaptation of Glass Mask, Alexis Rhodes in Yu-Gi-Oh! GX, Satsuki Kitaoji in Strawberry 100%, and Akira Okuzaki in the My-Hime and My-Otome series. She also took on the role of Reinforce in Magical Girl Lyrical Nanoha A's and provided voices for various characters in the Sonic X and Tsubasa: Reservoir Chronicle series.

A recurring and beloved role in her filmography is that of Reiko Natsume, the mysterious and powerful grandmother of the protagonist in the long-running Natsume's Book of Friends (Natsume Yūjin-Chō) series, a role she has played across multiple seasons, OVAs, and films since 2008. Her later work includes roles such as Namie Yagiri in Durarara!!, Canon Hazama in the Fafner franchise, and Rinko Kojirô in Sword Art Online: Alicization. In video games, she is known for voicing Gemini Sunrise in Sakura Wars: So Long, My Love and Kat in Gravity Rush.

Kobayashi has formed lasting friendships through her work. She became close with Megumi Toyoguchi, Mamiko Noto, and Nana Mizuki during their time on Strawberry 100%, a group they called the "Strawberry Party". She is also good friends with fellow voice actors Kenichi Suzumura, Takahiro Sakurai, and Shizuka Ito. Outside of voice acting, Kobayashi holds a black belt in kendo and has a passion for painting, having once considered pursuing a path in fine arts. Around 2007, her focus shifted more towards dubbing foreign films and television series, as well as stage work, though she continues to take on select anime roles.