As people around the globe began welcoming in 2011 with a glittering array of parties, Sydney's Harbour Bridge exploded in a spectacular blaze of New Year fireworks.
A fiery waterfall plunged from the landmark Australian structure as seven tonnes of fireworks ignited in the night sky, thrilling 1.5 million people crammed on the city's foreshore.
The celebrations follow devastating floods that have hit 200,000 in the country's northeast, muting the festivities there, while extreme heat prompted wildfire warnings around Melbourne and Adelaide.
Earlier, the 6,000 residents of the tiny Pacific nation of Kiribati, just east of the international dateline, were the first to see in the new year, while New Zealand's Auckland also marked the occasion with fireworks.
In Europe large crowds were set to throng landmarks like London's Big Ben and the Eiffel Tower, following a big freeze that paralysed travel and cut power and water supplies for tens of thousands.
And New York workers were scrambling to plough snow out of Times Square for the famous New Year countdown, after a blizzard dumped 32 inches (80 centimetres) on the city and surrounding areas.
As many as a million people -- monitored by a high-tech police presence -- were expected to mass in Times Square.
Party-goers carrying blankets and camping equipment began descending on Sydney harbour more than 12 hours before the main fireworks display, with new arrivals turned away as early as 3:00 pm (0400 GMT).
"It's absolutely beautiful," said Shirley Marlin, as she watched the pyrotechnics, while her husband Ron added: "We're very, very lucky to have this harbour."
In New Zealand's Christchurch, hit by a powerful earthquake in September, officials only approved celebrations after late checks and modifications, including removing the city cathedral's crucifix in case it fell on revellers.
In Asia hundreds of thousands of people gathered to watch a glittering fireworks-and-laser display along neon-lit Hong Kong's harbour. Dozens of boats also gathered in Victoria Harbour for the intense five-minute display.
In Japan millions of people visited Shinto shrines to "purify" themselves.
Although Lunar New Year is a much bigger event in the continent, thousands braved Beijing's cold for the countdown at an upmarket shopping centre, while about 7,000 people had been expected at a kite-flying event in central Shanghai.
In Myanmar democracy champion Aung San Suu Kyi, released this year after more than seven years of house arrest, called for the country's people "to struggle together with new strengths, new force and new words in the auspicious new year".
Police were on high alert for attacks in major cities in Pakistan, where New Year celebrations are traditionally quiet, private affairs.
Violence had flared earlier Friday as police and protesters clashed during a mass protest strike that closed businesses across the country over a bid to end the death penalty for blasphemy.
In the financial hub Karachi -- where police fired tear gas to quell demonstrations -- thousands of Pakistanis are set to celebrate the new year on the shores of the Arabian Sea.
Revellers in India's financial and entertainment capital Mumbai -- scene of a 2008 attack that killed 166 people -- were given the go-ahead to party through the night despite intelligence about a possible militant strike.
Despite chilly and misty weather, tens of thousands of people were expected to gather in London to watch the annual New Year's Eve fireworks display set against the backdrop of the London Eye big wheel.
However with the government's austerity measures set to bite early in 2011, a survey suggested that most Britons were planning low-key festivities to save money.
Elsewhere, millions will crowd landmarks like Rome's Colosseum and the Brandenburg Gate in Berlin, as well as Paris's Champs Elysees and the Puerta del Sol in Madrid.
Organisers were however forced to cancel a giant January 1 snowball fight in Berlin after 8,000 people signed up.