Masako Isobe is a Japanese actress and voice actress affiliated with the theatre company Gekidan Subaru. She was born on May 14, 1957, in Fukuoka Prefecture. Her career in the performing arts began on stage, and she has been a member of Gekidan Subaru since at least the early 1980s, appearing in numerous theatrical productions.

Her voice acting career encompasses a wide range of roles in anime, video games, and Japanese dubs of foreign films. In anime, she is known for voicing characters such as the Curator in Kino's Journey, Amaterasu Oomikami in Inari, Konkon, Koi Iroha, and Yoram Lavol in GANGSTA. She also played recurring roles in long-running series, voicing several different characters in the anime Detective Conan across multiple episodes in 1998, 2000, 2001, 2003, and 2005. In 2010, she voiced the role of the Company President in the Sunrise OVA Coicent. Her film work includes a role in the 1993 animated film Aoi Kioku - Manmō Kaitaku to Shōnen-tachi, where she voiced the character Suzuki Masae.

Isobe has an extensive career in voice-over work for foreign films and television series, providing the Japanese voice for a variety of actresses. Notable dubbing roles include the character of Aunt Bao in the Japanese dub of the film Kung Fu Hustle, Elena in Coco, and Roz in the Monsters, Inc. franchise. She has also dubbed the voices of actresses such as Kathy Bates and CCH Pounder in various projects.

A member of Gekidan Subaru for many years, she has collaborated with numerous fellow actors and voice actors from the company throughout her career. Her work is characterized by portrayals of authoritative female figures, including mentors, mothers, and elders. She brings a background in theatre and a proficiency in traditional arts, such as kimono dressing, to her professional work.