Fireworks, concerts and celebrations unfolded around the globe to ring in the new year and, for some, to wring out the old.
Hundreds of thousands of revellers crowded into New York City's Times Square to watch the crystal-covered ball make its annual descent.
New York City's countdown was the first in decades without television host Dick Clark, who died in April. One of the crystal panels on the ball was engraved with his name.
Elsewhere, lavish firework displays lit up skylines in Sydney, Hong Kong and Shanghai. In the United Arab Emirates city of Dubai, multi-coloured fireworks danced up and down the world's tallest building, the Burj Khalifa.
In Rome, Pope Benedict XVI celebrated New Year's Eve with a vespers service in St Peter's Basilica to give thanks for 2012 and look ahead to 2013. He said that despite all the death and injustice in the world, goodness prevailed.
In Russia, spectators filled Moscow's Red Square as fireworks exploded near the Kremlin. In Rio de Janeiro, revellers dressed head-to-toe in white as dictated by Brazilian new year's tradition flooded on to Copacabana beach for a concert.
Organisers said about 90,000 people gathered in a large field in Rangoon, Burma, for their first chance to do what much of the world does every December 31 - watch a countdown. The reformist government that took office in 2011 in the country, long under military rule, threw its first public new year's celebration in decades. "We feel like we are in a different world," said Yu Thawda, a university student who went with three of her friends.
Parts of Europe held scaled-back festivities and street parties, the mood a bit restrained - if hopeful - for a 2013 that is projected to be a sixth straight year of recession amid Greece's worst economic crisis since the Second World War. Often-soggy London stayed dry and clear as the familiar chimes of Big Ben counted down the final seconds of 2012 and a dazzling display of fireworks lit the skies above Parliament Square.
Elsewhere, the atmosphere of celebration was muted with concern. Hotels, clubs and other sites in New Delhi, the Indian capital, cancelled festivities after the death of a rape victim on Saturday sparked days of mourning and reflection about women's safety.