Ayatollah Shaykh Abdallah Mazandarani (Persian: عبدالله مازندرانی) (AD 1840–1912;[1] AH 1256–1330) was a Shia Marja' and a leader of the constitutional movement against the Qajar dynasty.

He played an important part in the constitutional movement, which included encouraging people to resist the Russian invasion and unfair contracts, and writing letters in support of the Islamic religion.

[5] Along with Mohammad Kazem Khorasani, Mazandarani protested against the policies and interference of the English government in the internal affairs of Iran.

[7] Akhund Khurasani, Mirza Husayn Tehrani and Shaykh Abdullah Mazandarani, theorised a model of religious secularism in the absence of Imam, that still prevails in Shia seminaries.

Mohammad Ali Shah wrote letters to the sources of emulation in Najaf, seeking their support against the perceived conspiracies of Babis and other heretics.