Osama Bin Laden was the leader and founder of al-Qaeda. For many years no-one knew exactly where he was, but he was found and in May 2011 was killed by American soldiers in Pakistan.
Osama Bin Laden was born in Saudi Arabia in 1957 to a wealthy family, and when his father died in a helicopter crash in 1968, the young Bin Laden inherited many millions of dollars.
In the 1980s, he fought against the Soviet Union, trying to force them out of Afghanistan. It was in this period that he founded al-Qaeda.
Afterwards, he became angry because he thought the US was interfering too much in the Middle East.
He had said it was the duty of all Muslims to fight against America and all its allies - though many Muslims believe what he was doing was very wrong.
He was thought to be behind a number of terrorist attacks in the 1990s.
On 11 September 2001 he masterminded the worst ever terror attack on American soil, when two planes were deliberately flown into the Twin Towers in New York, and he became the most wanted man in the world.