Grand Ayatollah Sayyid Muhammad-Sadiq al-Sadr (Arabic: محمّد صادق الصدر‎; born 23 March 1943 – 19 February 1999) was a prominent Iraqi Twelver Shiite cleric and marja'.

The growth of his popularity, often referred to as the followers of the local Hawza, also put him in competition with other Shi'a leaders, including Mohammed Baqir al-Hakim who was exiled in Iran.

In this ghetto, Sadr established a secret network of devoted followers and he became an increasingly prominent figure in the Iraqi political scene.

As a result of the disenfranchisement and repression of the Shi'ites in Iraq and the loyalty of the local populations, Saddam Hussein and his Baathist government could not control the Revolution Township on a neighbourhood level.

Sadr gained the support of the Shi'ites by reaching out to tribal villages and offering services to them that they would otherwise not have been afforded by Hussein's regime.

Anger at, among other things, the government's alleged involvement in Sadr's death helped spark the 1999 Shia uprising in Iraq.