Fadlallah had a wide following beyond Lebanon's Shiites, extending to Central Asia and the Gulf. He was a supporter of Iran's Islamic Revolution and the spiritual leader and mentor of the Shiite terror group Hezbollah in the first years after it was formed in 1982.
A fierce critic of the United States, Fadlallah used many of his Friday prayer sermons to denounce US policies in the Middle East, particularly its alliance with Israel.
He first praised US President Barack Obama for showing "sincerity" when he said the United States was not at war with Islam. However he later criticised the US administration, saying it had deluded Arabs and Muslims into believing it would chart a course away from the policies of former President George W. Bush. He was once a classmate of Iranian Supreme Leader Ayatollah Ali Khamenei.
He was known in Shiite religious circles for his moderate social views, especially on women. He issued several notable fatwas, or religious opinions, including banning the Shiite practice of shedding blood during Ashura.