Millions gathered on Brazil's Copacabana beach late Sunday to welcome 2018 in humid conditions – while a freezing North America prepared to close out the world's New Year celebrations.
A chilly Europe had already said goodbye to 2017, and the other side of the globe in Hong Kong and Sydney – where major celebrations began hours earlier – was already nursing a January 1st hangover after partying with dazzling firework displays.
The traditional pyrotechnics on Rio de Janeiro's beachfront got an extra blast this year, with a performance by Brazilian singer Anitta who gained worldwide recognition through a video of her in a mini-bikini performing "Vai Malandra" ("Come on bad girl").
"I am preparing a special show for you," she said on Twitter.
Bikinis were the last thing on the minds of North American revellers, who would follow Rio and South America in welcoming the New Year.
Much of the United States and Canada is bundled up to cope with unusually cold weather, including the roughly two million people gathered at New York's Times Square under the tightest security in years.
Most dressed in thick coats and snow gear, braced for a night tipped to be the coldest since 1962 – with temperatures of -10°C (14°F).
Britain's Big Ben rang
In London more than 100,000 ticket-holders gazed up at a spectacular pyrotechnics display from the banks of the River Thames, before dancing to "Auld Lang Syne".
Keeping with tradition, the Big Ben bell in the Houses of Parliament rang in Britain's new year. Although the clock tower is undergoing renovations, the chimes were turned back on especially for the celebrations.
In Britain, despite the capital being hit by four terror attacks in 2017, Scotland Yard said it had fewer police officers on the streets of London than during last year's event.
Other European cities were similarly awash with people despite the winter cold.
In Paris hundreds of thousands of partygoers braved a storm warning and drizzle to line the Champs-Élysées avenue before a dazzling light show and a fireworks display lit up the Arc de Triomphe.
Nearly 2,000 security forces were deployed to protect the crowd – out of about 140,000 mobilised nationwide to guard against the jihadist threat that authorities describe as "still high".
"Life goes on and they (jihadists) are on the retreat," said one reveller, who gave his name only as Stephane.
In Berlin, special tents were set up at the Brandenburg Gate to assist female victims of sexual harassment, following mass assaults on women in Cologne two years ago.
In Cologne itself, 1,400 police were mobilised, street lighting was improved and more video cameras were installed.
As the midnight chimes neared in western Europe, Hong Kong had already moved into 2018 with a stunning fireworks display over Victoria Harbour. Thousands watched as "shooting stars" were fired from the rooftops of skyscrapers during a musical spectacular.