Born to a family with a long line of top-ranking scholars that dominated the Hawza (Islamic seminaries) for many years in Karbala, Iraq. His family includes supreme religious jurists (Marja’a) such as the late Grand Ayatollah Mirza Mahdi Al Shirazi (grandfather), Grand Ayatollah Mohammad Shirazi (uncle) and Grand Ayatollah Sadiq Shirazi (uncle), late Grand Ayatullah Ali Al-Sabzowari (cousin), late Grand Ayatullah Sayed Abdul Hadi Al-Shirazi (great uncle), as well as Grand Ayatollah Mohammad Taqi Al Modarresi (brother).
Almodarresi started his religious education in the Islamic seminary of Karbala at the age of three and actively sought his religious studies under the auspices of many high ranking scholars. He completed the secondary part of the curriculum by the age of 9. Due to his distinguished abilities Ayatollah Almodarresi received the recognition of several Maraje’ who appointed him as their special representative. While engaged in preaching Islam in Bahrain and at the young age of 26 Grand Ayatollah Sabzewari and Grand Ayatollah Mar’ashi Najafi also awarded Ayatollah Almodarresi power of representation in which they praised him and labeled him as “scholar worthy of taking a leadership position” and urging Muslims to follow his lead.
Ayatollah Almodarresi's advocacy of political freedom and strong stance against Terrorism started from an early age when Saddam Hussein came to power. Seventeen members of his wife’s family have been executed by Saddam's regime or simply disappeared in the notorious Ba'th penitentiaries. The first book openly attacking the Iraqi regime ever to be published by a religious scholar was written by Ayatollah Almodarresi. Published under a pseudonym in Beirut, the book was titled No To Rulers of Iraq and sparked a massive political crisis in Baghdad and caused the Baathist regime to issue an ultimatum for the removal of all Lebanese nationals from Iraq within 72 hours.
Almodarresi eluded execution by moving from house to house, often living in cellars for months and traveling in disguise. His uncle Ayatollah Sayed Hassan Al Shirazi was gunned down by Iraqi government assassins in Beirut for his role as a key opposition figure to Saddam's regime.
With the escalation of the Ba’athist repression, Hadi fled Iraq and found sanctuary in Bahrain, which is where he rose to international prominence.
As a founding member of the Supreme Council for the Islamic Revolution in Iraq (SCIRI) and senior director of the Islamic Action Organization, Almodarresi was one of the most active figures of the Iraqi opposition in exile. While continuing his religious activities and adding over 250 published books to his CV, Hadi was closely involved in efforts to expose & bring down the regime in Baghdad. He was also able to escape a number of assassination attempts abroad including one in Brazil in 1991 as well as two more attempts against his life in Syria by Ba'athistTemplate:Clarification needed The Iraqi ones, not the Syrian ones? intelligence operatives in 2001.
Upon returning to Iraq after the fall of Saddam’s regime, he was greeted by over 30,000 people in Baghdad and 50,000 in Sadr City and a similar crowd in his native city of Karbala.
Ayatollah Almodarresi established a television station upon his return to his hometown. He is also involved in several large-scale humanitarian projects in Iraq and has been involved in the building of mosques, schools, medical clinics, orphanages, and has been a stanch advocate of women's rights and consistently speaks out against the oppression of women in his lectures and books. He also facilitates marriage by providing financial help to people who wish to get married and has organized several large mass marriage ceremonies. Modarresi also founded and currently heads the League of Religious Scholars which brings together many high ranking Shi’ite scholars or their representatives in Iraq.