Muhammad Baqir al-Sadr (آية الله العظمى السيد محمد باقر الصدر; 1 March 1935 – 9 April 1980), also known as al-Shahīd al-Khāmis (the fifth martyr), was an Iraqi philosopher, and the ideological founder of the Islamic Dawa Party, born in al-Kadhimiya, Iraq. He was father-in-law to Muqtada al-Sadr, a cousin of Muhammad Sadeq al-Sadr and Imam Musa as-Sadr. His father Haydar al-Sadr was a well-respected high-ranking Shi'a cleric. His lineage can be traced back to Muhammad through the seventh Shia Imam Musa al-Kazim. Muhammad Baqir al-Sadr was executed in 1980 by the regime of Saddam Hussein along with his sister, Amina Sadr bint al-Huda.
Muhammad Baqir al-Sadr was born in al-Kazimiya, Iraq to the prominent Sadr family, which originated from Jabal Amel in Lebanon. His father died in 1937, leaving the family destitute. In 1945, the family moved to the holy city of Najaf, where al-Sadr would spend the rest of his life. He was a child prodigy who, at 10, was delivering lectures on Islamic history. At eleven, he was a student of logic. He wrote a book criticizing materialist philosophy when he was 24. Al-Sadr completed his religious studies at religious seminaries under al-Khoei and Muhsin al-Hakim, and began teaching at the age of 25.
Al-Sadr's works attracted the ire of the Baath Party leading to repeated imprisonment where he was often tortured. Despite this, he continued his work after being released. When the Baathists arrested Ayatollah Al-Sadr in 1977, his sister Amina Sadr bint al-Huda made a speech in the Imam Ali mosque in Najaf inviting the people to demonstrate. Many demonstrations were held, forcing the Baathists to release Al-Sadr who was placed under house arrest.
In 1979–1980, anti-Ba'ath riots arose in Iraq's Shia areas by groups who were working toward an Islamic revolution in their country. Saddam and his deputies believed that the riots had been inspired by the Iranian Revolution and instigated by Iran's government. In the aftermath of Iran's revolution, Iraq's Shia community called on Mohammad Baqir al-Sadr to be their “Iraqi Ayatollah Khomeini”, leading a revolt against the Ba'ath regime.