Moammar Gadhafi was in power from 1969 after he deposed King Idris in a military coup until National Transitional Council fighters overran his compound in August.
National Transitional Council officials say the former Libyan leader was reportedly killed Wednesday as transitional fighters took control of Gadhafi's hometown.
Sirte was the last remaining bastion controlled by Gadhafi loyalist.
Colonel Gadhafi gained a reputation as an eccentric, donning flowing robes and animal skins and surrounding himself with all female bodyguards.
Labeled the "mad dog of the Middle East" by former U.S. President Ronald Reagan, the Libyan leader drew attention for his often-controversial political decisions.
He has supported a number of revolutionary movements around the world, including in Chad and Iran. He has been accused of sponsoring Islamic militant groups and terrorist attacks.
In 1986, U.S. President Reagan ordered air strikes in Libya because of the Gadhafi government's alleged involvement in the bombing of a German nightclub that killed two U.S. servicemen. Gadhafi's adopted daughter died in the U.S. raid.
Just two years later, Libya was blamed for the bombing of Pan Am flight 103 over the Scottish town of Lockerbie that killed 270 people. Gadhafi admitted responsibility for the attack in 2003 and agreed to pay victims' families more than $2 billion in compensation.
That same year, the Libyan leader agreed to renounce terrorism and weapons of mass destruction, clearing the way for the lifting of U.S. and European sanctions imposed after the German disco bombing, and the restoring of diplomatic relations. The United Nations also lifted its sanctions related to the Lockerbie bombing.
But the goodwill did not last long. Gadhafi fought to hold onto power against a large-scale uprising that began in February. He was under immense international pressure to step down after responding to the uprising with deadly violence. The government crackdown on protesters prompted new international sanctions against Libya, and in March, NATO began an air campaign against Gadhafi's forces under a U.N. mandate to protect the Libyan people.
Born in 1942 to a Bedouin family in the Libyan desert, Gadhafi graduated from the University of Libya and became an army officer.
Less than a decade after taking control of the country at age 27, he invented a system of government called the "Jamahiriya," Arabic for "state of the masses." In theory, the system was to be run by people's committees, with Gadhafi assuming the title of "Brotherly Leader and Guide of the Revolution." But in reality, he quashed dissent and reportedly survived several assassination attempts.
Gadhafi was a strong advocate of the ideology of Arab unity known as Pan-Arabism, and also led a Pan-African effort seeking to unify African nations.