Revellers around the world welcomed 2013 with dancing, singing and firework spectaculars.
In London, thousands flocked to the Thames to witness the display of pyrotechnics and lights.
Another huge crowd descended on Edinburgh for the world-famous Hogmanay celebrations with rock band Simple Minds headlining a concert and the ramparts of Edinburgh Castle forming the backdrop for the fireworks.
There were similar scenes around the world as cities competed to put on the most spectacular shows.
London's looked back, with the 2012 Olympic Games and the Queen's Diamond Jubilee celebrations featuring in a display over the London Eye which Mayor of London Boris Johnson described as "an amazing end to an incredible year".
Asian cities kicked off New Year's celebrations in an atmosphere of renewed optimism, despite the "fiscal cliff" economic impasse threatening to reverberate globally from the United States.
Huge fireworks lit up skylines in Sydney, Hong Kong and Shanghai, and even the once-isolated country of Burma joined the countdown party for the first time in decades.
In Dubai, the Burj Khalifa, the world's tallest building, was lit up with hundreds of fireworks.
In Russia, Moscow's Red Square was filled with spectators as fireworks exploded near the Kremlin to welcome in the new year.
In austerity-hit Europe, the mood was more restrained - if hopeful. The year 2013 is projected to be a sixth straight one of recession amid Greece's worst economic crisis since the second World War.
In fact, the new year was starting with a 24-hour strike by subway and train workers in Athens over salary cuts that are part of the government's austerity measures.
Still, in his televised New Year's Eve message, Prime Minister Antonis Samaras promised Greeks that the worst of the crisis is past, and declared 2013 a "year of hope" that will see the beginning of the country's rebirth.
German Chancellor Angela Merkel's New Year's message warned her country to prepare for difficult economic times ahead.
It was a busy night for the emergency services, with some reporting a huge spike in the number of calls they received.
South East Coast Ambulance Service (Secamb), which handles 999 calls from Kent, Sussex and Surrey, took 1,544 calls between 10pm yesterday and 4am this morning - a rise of more than 20% on the same period last year.
Yesterday, Secamb officials urged people to use the service wisely and only call when absolutely necessary.
Last year a large number of calls were due to people falling over, suffering breathing difficulties or being injured in fights.
West Midlands Ambulance Service saw its peak for 999 calls between 1am and 4am.
The service said it handled 1,291 calls between midnight and 5am, a 9% increase on the same period last year, while 638 calls were taken in the four hours leading up to midnight - a 15% rise on the same period the previous year.
A spokeswoman said a large proportion of this year's calls were for alcohol-related incidents including fights, assaults, falls and overdoses.
One incident in Stourbridge saw four people rescued from a river after three friends tried to help a drunken teenage girl from the water after she fell down a bank just after 8pm.