Thousands of revellers have taken to the streets across the UK to herald the new year.
Hundreds of thousands gathered in London to watch the 11-minute fireworks display under the London Eye, triggered by Big Ben's chimes.
In Cardiff there was free live music at the Civic Centre, but no outdoor concert in Belfast this year.
People attended events across Scotland, including some 80,000 in Edinburgh for the Hogmanay street party celebrations.
Around 3,000 police officers were on duty in London, both at street level and on podiums, to give them a bird's-eye view of any troublemakers.
But Scotland Yard said it had been a "fairly quiet" night with 77 arrests as of 04:30 GMT, mostly for public order or drunk and disorderly offences.
As midnight struck, it triggered a display of some 12,000 fireworks at the London Eye - producing 50,000 projectiles.
Some were fired from the Houses of Parliament itself, to coincide with each strike of Big Ben.
There was a 2012 Games theme to the spectacle, with many fireworks in the shape and colours of the Olympic rings.
Mayor of London Boris Johnson said: "Our New Year fireworks were a brilliant start to a spectacular year.
"This is just the beginning - as the eyes of the world turn to London for the Olympic and Paralympic Games."
Meanwhile, about 20,000 revellers gathered in the centre of Weymouth, Dorset, for its New Year's Eve fancy dress party. The event has been running for the past 20 years.
Cardiff's annual Calennig celebrations at the Civic Centre also featured a firework display at midnight.
In the absence of an official city council-run event, revellers in Belfast were advised by the council to attend events in local clubs and pubs.
Some 80,000 people gathered in Princes Street, Edinburgh, to see in the new year at the city's world-famous Hogmanay street party.
Around 5.5 tonnes of fireworks lit up the sky above the castle - the most ever for a Hogmanay celebration.
More than 2,800 individual fireworks were used to produce the six-minute display.
And more than 20 acts performed on seven stages ahead of the midnight display.
A huge free party was held in Inverness, while in Aberdeen a free fireworks display was set off from the roof of His Majesty's Theatre in the city centre.
Glasgow hosted a family day, which ended at 22:00 GMT, with traditional music and children's activities.
The city council had previously said it was not holding a street party this year due to the cost.