Crowds of people had gathered in front of the White House amid rumours of a major event.
Details of how Bin Laden was tracked down and killed are now emerging. He was found at a fortified compound on the outskirts of Abbottabad in north-west Pakistan.
Obama announced that the operation had been in the planning stages since August 2010, and that last week he had personally given the green light to go and get Bin Laden.
US suspicions had been originally been aroused by the fact that such a heavily fortified building had no internet access or telephone lines.
The compound was just 600 metres from the Pakistan Military Academy, raising questions about how much the Pakistani authorities knew of Bin Laden's hiding place.
The operation began at about 2230 and lasted around 45 minutes according to military sources.
Witnesses say helicopters were seen flying low over the area, and people living nearby were told to turn off their lights and stay in their homes.
The walls around the compound were 14 metres high, so no action was visible to outsiders, and after the operation locals said they could see flames snaking up from inside the building.
Pakistani troops arrived at the scene after the operation and have now completely taken over the area.