A massive fireworks display has lit up Sydney Harbour as Australia’s largest city ushered in 2017.
Some 1.5 million revellers had been expected to turn out on the waterfront.
Earlier, Auckland in New Zealand has become the first major world city to welcome the New Year.
Many cities around the world have stepped up security for New Year’s Eve celebrations, after a year in which attackers drove lorries into crowds in Berlin in Germany and Nice, France.
Thousands of extra police will be on duty in London and other cities.
In Paris, Madrid and New York, concrete barriers and heavy goods vehicles will be used to block off central squares where crowds gather to celebrate.
The midnight fireworks display at Sydney Harbour paid tribute to Prince and David Bowie, two music superstars who died in 2016.
“This year, sadly, we saw the loss of many music and entertainment legends around the world,” fireworks co-producer Catherine Flanagan said.
“So celebrating their music as part of Sydney New Year’s Eve fireworks displays is an opportunity to reflect on the year that has been and what the future may hold.”
Pacific islands including Samoa, Tonga and Kiribati entered 2017 at 10:00 GMT, followed an hour later by Auckland, where fireworks erupted from the 328m (1,080ft) tall Sky Tower in the city centre.
On Friday a man in Sydney was charged in connection with threats made against Sydney’s New Year’s Eve celebrations.
Police said he was charged with a “crimes act offence, but not a terrorist offence” and there was no continuing threat to the community.
Israel has also warned its citizens travelling in India to avoid crowds, saying there is a risk of imminent “terrorist attacks”.
Celebrations in some European cities were overshadowed by security arrangements last year.
In Cologne, Germany, about 1,500 extra police officers will be deployed at the city’s New Year’s Eve events.
It is a year since scores of women reported being assaulted, groped and in one case raped by men they described as being of Arab or North African appearance.
At the time the justice minister warned against linking the crimes to the issue of migrants and refugees, and for this year’s celebration, two extremist far-right groups have been banned from holding rallies. The police cited security reasons.
Meanwhile, a “leap second” will be added to the countdown to compensate for a slowdown in the Earth’s rotation.
The extra second will occur as clocks strike midnight and a time of 23:59:60 GMT will be recorded, delaying 2017 momentarily.
It will only affect countdowns in countries using Greenwich Mean Time, which includes Britain.
This is required because standard time lags behind atomic clocks.