Bin Laden, 54, approved the 9/11 attacks in which nearly 3,000 people died.
He evaded the forces of the US and its allies for almost a decade, despite a $25m (£15m) bounty on his head.
Mr Obama said he had been briefed last August on a possible lead to Bin Laden's whereabouts. He authorised the operation last week once he determined there was enough intelligence to take action.
"It was far from certain, and it took many months to run this thread to ground," Mr Obama said.
On Sunday, US forces said to be from the elite Navy Seal Team Six undertook the operation in Abbottabad, 100km (62 miles) north-east of Islamabad.
US officials said Bin Laden was shot in the head after resisting.
Mr Obama said "no Americans were harmed".
US media reports said that the body was buried at sea to conform with Islamic practice of a burial within 24 hours and to prevent any grave becoming a shrine.
Giving more details of the raid, one senior US official said a small US team conducted the attack in about 40 minutes.
Three other men - one of Bin Laden's sons and two couriers - were killed in the raid, the official said, adding that one woman was also killed when she was used as "a shield" and two other women were injured.
One helicopter was lost due to "technical failure". The team destroyed it and left in its other aircraft.
One resident, Nasir Khan, told Reuters the helicopters had come under "intense firing" from the ground.
The size and complexity of the structure in Abbottabad "shocked" US officials.
It was surrounded by 4m-6m (12ft-18ft) walls, was eight times larger than other homes in the area and was valued at "a million dollars", though it had no telephone or internet connection.
The US official said that intelligence had been tracking a "trusted courier" of Bin Laden for many years. The courier's identity was discovered four years ago, his area of operation two years ago and then, last August, his residence in Abbottabad was found, triggering the start of the mission.
Another senior US official said that no intelligence had been shared with any country, including Pakistan, ahead of the raid.
"Only a very small group of people inside our own government knew of this operation in advance," the official said.
The Abbottabad residence is just a few hundred metres from the Pakistan Military Academy - the country's equivalent of West Point or Sandhurst.
The BBC's Aleem Maqbool in Abbottabad says it will undoubtedly be a huge embarrassment to Pakistan that Bin Laden was found not only in the country, but also on the doorstep of the military academy.
He says residents in the town were stunned the al-Qaeda leader had been living in their midst.
The senior US official said the "the loss of Bin Laden puts the group on a path of decline that will be difficult to reverse".
Bin Laden's probable successor, Ayman al-Zawahiri, was "far less charismatic and not as well respected within the organisation", according to reports from captured al-Qaeda operatives, the official said.
However, the root causes of radical Islam - the range of issues that enabled al-Qaeda to recruit disaffected young Muslims to its cause - remain, for the most part, unaddressed, Islamic affairs analyst Roger Hardy told the BBC.
"The death of Bin Laden will strike at the morale of the global jihad, but is unlikely to end it," he warned.
Bin Laden killed: How it happened
More details have now emerged of how al-Qaeda leader Osama Bin Laden was found and killed at a fortified compound on the outskirts of Abbottabad in north-west Pakistan.
The compound is a few hundred metres from the Pakistan Military Academy, an elite military training centre, which is being described as Pakistan's equivalent to Britain's Sandhurst or the West Point academy in the US.
There were conflicting reports about the compound's distance from the academy, with Pakistan's military saying they are as much as 4km (2.4 miles) apart.
In any case the compound lies well within Abbottabad's military cantonment, and it is likely the area would have had a constant and significant military presence and checkpoints.
Pakistan's army chief is a regular visitor to the academy, where he attends graduation parades.
The operation against Osama Bin Laden began at about 2230 (1730 GMT) and lasted about 45 minutes, military sources told BBC Urdu. Two or three helicopters were seen flying low over the area. Witnesses say they caused panic among local residents.
One report of the operation emerged in real-time: Sohaib Athar, an IT consultant living in Abbottabad, posted on Twitter at about 0100 (2100 GMT) that a helicopter was hovering above the city.
He continued tweeting as the operation unfolded before eventually realising: "Uh oh, now I'm the guy who liveblogged the Osama raid without knowing it.
Barbed wire and cameras
The target of the operation was the compound, which had at its centre a large three-storey building.
When the helicopters - which had reportedly flown from Afghanistan - landed outside the compound, men emerged from the aircraft. The raid was conducted by a special team of between 20 and 25 US Navy Seals. Counter-Terrorism advisor John Brennan: "The minutes passed like days"
People living in the area, known as Thanda Choha, told BBC Urdu that they were commanded in Pashto to switch off their lights and not to leave their homes.
Shortly afterwards residents said they heard shots being fired and the sound of heavy firearms.
At some point in the operation one of the helicopters crashed, either from technical failure or having been hit by gunfire from the ground. But no US commandos were injured.
The compound was about 3,000 sq yds in size but people from the area told the BBC that it was surrounded by 14ft-high walls, so not much could be seen of what was happening inside.
The walls were topped by barbed wire and contained cameras.
There were two security gates at the compound - said to have been valued at about $1m (£600,000) - but no phone or internet lines running into the building.
Its occupants were so concerned about security that they were reported to burn their rubbish rather than leave it out for collection as other residents in the area did.
'Waziristan Mansion'
After the operation witnesses said all they could see was fire snaking up from inside the house.
Osama Bin Laden did resist the assault and was killed in battle, US officials told White House reporters. The al-Qaeda leader was shot in the head.
Abbottabad
Abbottabad - known as "city of pines"- is a small town nestled in the beautiful lush, green hills of north-west Pakistan.
It is an agricultural community, but with a population of about 120,000, it provides a centre for many of the neighbouring villages
It is a military garrison town and has one of Pakistan's most prestigious training academies
It takes its name from British Major James Abbott who founded it in 1853 after he annexed the Punjab area
The officials described the operation as a "surgical raid" and said three adult males, including Bin Laden's adult son, were killed. But, they added, a woman who was being used as a shield was also killed.
According to local residents speaking to BBC Urdu the forces conducting the operation later emerged from the compound, possibly with somebody who had been inside.
Some reports say Bin Laden's body was then flown to Afghanistan before eventually being laid to rest at sea.
Local residents say that women and children were also living in the compound.
One local resident told the BBC Urdu that the house had been built by a Pashtun man about 10 or 12 years ago. The resident said that none of the locals were aware of who was really living there. However, the New York Times said US officials believed that the house was specially built in 2005.
According to one local journalist, the house was known in the area as Waziristani Haveli - or Waziristan Mansion.
The journalist said it was owned by people from Waziristan, the mountainous and inhospitable semi-autonomous tribal area close to the Afghan border, which until now most observers believed to be Bin Laden's hiding place.
This house was in a residential district of Abbottabad's suburbs called Bilal Town and known to be home to a number of retired military officers from the area.
Intelligence officials in the US are quoted by AP as saying that the house was custom-built to harbour a major "terrorist" figure.
'Trusted' courier
As details of the raid emerged it became clear that the operation had been long in the planning. US officials said they received intelligence that Osama Bin Laden might be in that compound as long ago as last summer.
CIA experts analysed whether the "high value target" living at the compound could be anyone else but they decided in the end that it was almost certainly Bin Laden.
AdvertisementFootage from inside Bin Laden's compound
US intelligence agents focussed in particular on one of Bin Laden's couriers - a man identified as a protege of captured al-Qaeda commander Khalid Sheikh Mohammed. The courier's pseudonym was reportedly given to US interrogators by detainees at Guantanamo Bay in Cuba, US media reported.
He appeared to be one of the few couriers completely trusted by Osama Bin Laden, who helped keep the al-Qaeda figurehead in touch with the rest of the world.
For years US intelligence had been unable to name the courier. But four years ago they worked out who he was and two years later they discovered where he operated.
It was only in August 2010 that they located him in Abbottabad, Pakistan.
The order to carry out the mission was finally given by President Obama last Friday, after he had held five National Security Council meetings in March and April.
US officials described as "extraordinary" the security measures in the Abbottabad compound - among them high walls and barricades, very few windows, and a 7ft high privacy wall on the second floor.
After the US attack Pakistani troops arrived at the scene and secured the area.
