"Justice has been done," Obama said in a late-night address to the nation from the White House.
Bin Laden, the world's most wanted man, died in a firefight with U.S. Navy Seals at his compound in the northern Pakistani city of Abottabad.
"The United States has conducted an operation that killed Osama bin Laden, the leader of al Qaeda, and a terrorist who's responsible for the murder of thousands of innocent men, women, and children," Obama said.
Bin Laden was shot in the head during the 40-minute operation, which left three other men, including one of his sons, dead, U.S. officials said.
"A small team of Americans carried out the operation with extraordinary courage and capability. No Americans were harmed. They took care to avoid civilian casualties. After a firefight, they killed Osama bin Laden and took custody of his body," the president said.
The terrorist leader's body was identified and later buried at sea, U.S. media reports said.
"It was nearly 10 years ago that a bright September day was darkened by the worst attack on the American people in our history. The images of 9/11 are seared into our national memory -- hijacked planes cutting through a cloudless September sky; the Twin Towers collapsing to the ground; black smoke billowing up from the Pentagon; the wreckage of Flight 93 in Shanksville, Pennsylvania, where the actions of heroic citizens saved even more heartbreak and destruction," Obama said.
The Sept. 11, 2001, terrorist attacks on New York and Washington killed some 3,000 people and led former U.S. President George W. Bush to launch a global war on terror.
Al Qaeda has been accused of mounting numerous attacks around the world since 2001.