Grand Ayatollah Hossein Mazaheri Isfahani (; born 16 November 1933) is an Iranian senior Twelver Shia Marja. He was also a member of the Third Assembly of Experts.
Grand Ayatollah Hossein Mazaheri was born in Isfahan in 1933. At the age of 14, he moved to Isfahan Seminary to start his religious studies. Five years later, he moved to Qom to complete his studies. In Qom he studied in Seminars of Grand Ayatollah Boroujerdi and Imam Khomeini. Ayatollah Marashi Najafi, Allamah Tabatabei and Mohaqeq Damad were also among his teachers. He currently resides and teaches in the Seminary of Isfahan, Iran.