Wow. My beard just came back.
Bin Laden was killed in a ground operation outside Islamabad based on US intelligence, the first lead for which emerged last August.
Mr Obama said after "a firefight", US forces took possession of the body.
Bin Laden is believed to be the mastermind of the attacks on New York and Washington on 11 September 2001 and a number of others.
He was top of the US' "most wanted" list.
Mr Obama said it was "the most significant achievement to date in our nation's effort to defeat al-Qaeda".
The US has put its embassies around the world on alert, warning Americans of the possibility of al-Qaeda reprisal attacks for Bin Laden's killing.
Crowds gathered outside the White House in Washington DC, chanting "USA, USA" after the news emerged.
A US official quoted by Associated Press news agency said Bin Laden's body had been buried at sea, although this has not been confirmed.