Osama Bin Laden is both one of the CIA's most wanted men, and a hero for many young people in the Arab world.
He and his associates are being sought by the US on charges of international terrorism, including in connection with the 1998 bombing of American embassies in Africa and this year's attack on the USS Cole in Yemen.
In May this year a US jury convicted four men believed to be linked with Mr Bin Laden of plotting the embassy bombings in Kenya and Tanzania.
Mr Bin Laden, an immensely wealthy and private man, has been granted a safe haven by Afghanistan's ruling Taleban movement.
During his time in hiding, he has called for a holy war against the US, and for the killing of Americans and Jews. He is reported to be able to rally around him up to 3,000 fighters.
He is also suspected of helping to set up Islamic training centres to prepare soldiers to fight in Chechnya and other parts of the former Soviet Union.
Sponsored by US and Pakistan
His power is founded on a personal fortune earned by his family's construction business in Saudi Arabia.
Born in Saudi Arabia to a Yemeni family, Mr Bin Laden left Saudi Arabia in 1979 to fight against the Soviet invasion of Afghanistan.
The Afghan jihad was backed with American dollars and had the blessing of the governments of Saudi Arabia and Pakistan.
He received security training from the CIA itself,
according to Middle Eastern analyst Hazhir Teimourian.
While in Afghanistan, he founded the Maktab al-Khidimat (MAK), which recruited fighters from around the world and imported equipment to aid the Afghan resistance against the Soviet army.
Egyptians, Lebanese, Turks and others - numbering thousands in Mr Bin Laden's estimate - joined their Afghan Muslim brothers in the struggle against an ideology that spurned religion.
Turned against the US
After the Soviet withdrawal, the "Arab Afghans", as Mr Bin Laden's faction came to be called, turned their fire against the US and its allies in the Middle East.
Mr Bin Laden returned to Saudi Arabia to work in the family construction business, but was expelled in 1991 because of his anti-government activities there.
He spent the next five years in Sudan until US pressure prompted the Sudanese Government to expel him, whereupon Mr Bin Laden returned to Afghanistan.
Terrorism experts say Mr Bin Laden has been using his millions to fund attacks against the US.
The US State Department calls him "one of the most significant sponsors of Islamic extremist activities in the world today".
According to the US, Mr Bin Laden was involved in at least three major attacks - the 1993 World Trade Center bombing, the 1996 killing of 19 US soldiers in Saudi Arabia, and the 1998 bombings in Kenya and Tanzania.
Islamic front
BBC correspondent James Robbins says Mr Bin Laden had "all but admitted involvement" in the Saudi Arabia killings.
Some experts say he is part of an international Islamic front, bringing together Saudi, Egyptian and other groups.
Their rallying cry is the liberation of Islam's three holiest places - Mecca, Medina and Jerusalem.
The few outsiders who have met Osama Bin Laden describe him as modest, almost shy. He rarely gives interviews.
He is believed to be in his 40s, and to have at least three wives.
