Mohammed Kazem Yazdi (1831 – April 1919) was a prominent Shia Islamic scholar centered in Najaf, most famous for his anti-constitutionalist stand during the Iranian Constitutional Revolution of 1905–1911. He is said to have at first reflected the attitude of the "piously apolitical ulama" and refused to take a stand in favor of the Constitution despite insistent pressure by pro-Constitution talebs, but then opposed the Constitution siding with Sheikh Fazlollah Noori when Noori's son came to Najaf to enlist clerical support.
In the ensuing reaction against the politicized students in Najaf and the execution of Noori, Yazdi was supported by his Arab followers, the Ottoman governor, and the group known as the "Army of God" (jond Allah). His victory over the Constitutionalists and their clerical leader Mohammad-Kazem Khorasani was "complete," with Yazdi emerging as "the undisputed master of the Holy Cities." According to secular historian Ahmad Kasravi, several thousand would pray behind Yazdi at salat but only 30 or so prayed behind his rival Khorasani.