Colonel Gaddafi is the longest-serving leader in both Africa and the Arab world, having ruled Libya since he toppled King Idris I in a bloodless coup in 1969 aged 27.
Col Gaddafi presents himself as the spiritual guide of Libya
He may be ridiculed by some for his flamboyant dress-sense and female bodyguards, but Col Gaddafi is also a skilled political operator who moved swiftly to bring his country out of diplomatic isolation.
It was in 2003 - after some two decades of pariah status - that Tripoli took responsibility for the bombing of a Pan Am plane over the Scottish town of Lockerbie, paving the way for the UN to lift sanctions.
Months later, Col Gadaffi's regime abandoned efforts to develop weapons of mass destruction, triggering a fuller rapprochement with the West.
That saw him complete a transition from international outcast to an accepted, if unpredictable, leader.
Muammar Gaddafi was born in the desert near Sirte in 1942, and in his youth he was an admirer of Egyptian leader and Arab nationalist Gamal Abdel Nasser.
He first hatched plans to topple the monarchy at military college. He went to Britain for further army training before returning to the Libyan city of Benghazi and launching his coup there on September 1, 1969.
He laid out his political philosophy in the 1970s in his Green Book, which charted a home-grown alternative to both socialism and capitalism, combined with aspects of Islam.
On foreign trips he sets up camp in a luxury Bedouin tent and is accompanied by armed female bodyguards - he says they are less easily distracted than their male counterparts.
A tent is also used to receive visitors in Libya, where Col Gaddafi sits through meetings or interviews swishing the air with a horsehair or palm leaf fly-swatter.
The international community's rejection of Libya centred on Col Gaddafi's backing for a number of militant groups, including the Irish Republican Army and the Palestine Liberation Organisation.
US president Ronald Reagan labelled him a "mad dog", and the US responded to Libya's alleged involvement in attacks in Europe with airstrikes on Tripoli and Benghazi in 1986.
Col Gaddafi was said to be badly shaken by the bombings, in which his adopted daughter was killed.
Spurned in his efforts to unite the Arab world, from the 1990s Col Gaddafi turned his gaze towards Africa, proposing a "United States" for the continent.
He adopted his dress accordingly, sporting clothes that carried emblems of the African continent or portraits of African leaders.
At the turn of the millennium, with Libya struggling under sanctions, he began to bring his country in from the cold.
It took several years but he achieved his goal and in 2008 reached a final compensation agreement over Lockerbie and other bombings, allowing normal ties with Washington to be restored.
"There will be no more wars, raids, or acts of terrorism," he said at the time.
At home, the Libyan leader presents himself as the spiritual guide of the nation, overseeing what he says is a version of direct democracy.
In practice, critics say, he has retained absolute power. Dissent has been ruthlessly crushed and the media remains under strict government control.
Human Rights Watch says hundreds of people have been imprisoned for opposing him, with some sentenced to death. Torture and disappearances have also been reported.
Although Libya's economy has been opened up to foreign investment, there has been little in the way of reform.
Many Libyans feel they have not benefited from the country's vast oil and gas reserves, with public services poor and corruption rife.
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