Born in 1960 in East Beirut, Nasrallah from a young age was described as a remarkable student devoted to the teachings of Islam.
In 1975, the Lebanese civil war forced his family to return to their ancestral home in the south Lebanon village of Bazzouriyeh.
There Nasrallah, 15, joined the Amal movement, a political and paramilitary organisation representing Shia in Lebanon.
From south Lebanon, young Nasrallah travelled to Najaf, Iraq, for Quranic studies at a seminary.
In 1978, Nasrallah and other Shia clerics and students considered by the Baath government to be "radical" were forced to leave Iraq and return to Lebanon.
Nasrallah then studied and taught at Amal leader Sheikh Abbas al-Musawi's school.
Rise of Hezbollah
In 1982, after the Israeli invasion, Nasrallah followed Musawi out of Amal and into an umbrella organisation called Hezbollah.
Hezbollah is backed by Iran.
In 1992, the Israeli military assassinated al-Musawi along with his wife and three children.
Hezbollah is widely credited with
evicting Israel from Lebanon
Nasrallah, at the request of Iran's Ayatollah Ali Khamenei, took over the movement's leadership.
Under Nasrallah's leadership, Hezbollah became a serious opponent of the Israeli forces in southern Lebanon.
His standing in the country was strengthened after his son was killed by Israeli forces in 1996.
Hezbollah attacks on the Israeli armed forces were an important factor in Israel's decision to withdraw from south Lebanon in 2000.
The achievement has greatly bolstered the party's national political standing.
After the Israeli withdrawal, Nasrallah was at the helm of a complex exchange of prisoners with Israel, resulting in hundreds of Palestinian and Hezbollah members being freed and bodies of fighters returned to Lebanon.
"I don't believe in the state of Israel as a legal state because it was founded on occupation"
Sayed Hassan Nasrallah
Hezbollah's position, along with that of Syria and the Lebanese government, is that the Israeli withdrawal from Lebanon is not complete, with Lebanon claiming sovereignty over the Shebaa Farms.
The UN says the border area is an Israeli-occupied Syrian land unless Beirut and Damascus amend their border.
Nasrallah continues to call for the "continued resistance" against Israeli occupation of Lebanon.
He is also a strong opponent of the state of Israel.
"I don't believe in the state of Israel as a legal state because it was founded on occupation," he said in an interview in 2000.
Nasrallah, who lives in south Beirut, is married and has three children.
The Hezbollah chief is said to enjoy reading the memoirs of political figures. He has read Ariel Sharon's autobiography, as well as Binyamin Netanyahu's A Place Under the Sun.