Noriko Nagai is a Japanese voice actress known for a career that has spanned from the mid-1980s to the present day. She is also widely recognized by her professional stage name, Noriko Hidaka. Her legal name, Noriko Nagai, reflects her married name, and she was born Noriko Ito on May 31, 1962, in the Chiyoda ward of Tokyo, Japan.

Before committing to voice acting, Nagai began her entertainment career as an idol singer while in high school, releasing music under her birth name. However, she transitioned to voice work, making her anime debut in 1984. Her career reached a turning point in 1985 when she was cast as Minami Asakura, the heroine of the popular baseball romance series Touch. This early lead role brought her significant recognition and established her reputation in the industry.

Nagai is celebrated for her versatility, having portrayed a wide range of characters including young heroines, boys, and mature women. One of her most beloved early roles is Satsuki Kusakabe in Hayao Miyazaki's classic film My Neighbor Totoro (1988). The same year, she also took on the lead role of Noriko Takaya in the seminal science fiction OVA series Gunbuster. In 1989, she began voicing Akane Tendo, the spirited female lead in the long-running martial arts comedy Ranma 1/2, a role she continues to reprise in new adaptations decades later. The early 1990s saw her take on the part of Mikage Matsunaga in the series Miracle Girls (1993). Her skill at portraying youthful male characters is exemplified by her performances as Jean Roque Raltique in Nadia: The Secret of Blue Water (1990) and as the polite but deadly swordsman Seta Sojiro in Rurouni Kenshin (1996).

Throughout the 2000s and beyond, Noriko Nagai continued to take on prominent and diverse roles. She gave a memorable performance as the tragic priestess Kikyo in Inuyasha (2000), and later as the cunning and childlike antagonist Near in Death Note (2006). She also voiced the beloved matriarchal figure Belle-Mere in One Piece (2000) and, in a later part of her career, began voicing the high school detective Masumi Sera in the long-running series Case Closed (known as Detective Conan) starting in 2012. Her role as the magical mentor Shiny Chariot in Little Witch Academia (2017) introduced her work to a new generation of anime fans.

Over the course of her lengthy career, Nagai has formed several notable recurring collaborations. She worked extensively with director Hideaki Anno in his early career, providing the lead voices for his works Gunbuster and Nadia: The Secret of Blue Water. She has also been a consistent presence in adaptations of Rumiko Takahashi's manga, primarily as Akane Tendo in Ranma 1/2 and as Kikyo in Inuyasha. Furthermore, she has voiced characters in multiple entries of the Pokémon film series.

Her body of work has earned her significant acclaim. She is frequently cited as one of the most talented and popular voice actors of her generation, and she has been recognized as a key figure in the first wave of voice actor idolization in Japan. In 2009, she co-founded the talent agency Combination, where she continues her work as a voice actress and narrator. Her career, marked by iconic roles that span multiple decades, has solidified her status as a distinguished and enduring figure in the anime industry.