Smoke-choked Sydney ushered in the New Year with a huge fireworks display, kicking off celebrations for billions around the world and ringing in the new decade.
Australia's largest city usually puts on a dazzling display of pyrotechnics over the glittering harbour, but this year there have been calls to cancel the fireworks as devastating bushfires rage across the country.
Fireworks displays were scrapped in Australia's capital, Canberra, and Sydney's western suburbs because of elevated fire danger and extreme weather conditions.
As the clock ticked past midnight, major cities in Asia, Europe, Africa and the Americas embraced the celebrations.
Midnight in London was marked by the chimes of Big Ben, which has been silent during a long restoration, as traditional fireworks are set off over the Thames for the last new year before Brexit.
Thousands lined the Thames to watch fireworks explode over the London Eye, Westminster Abbey and Elizabeth Tower near Parliament.
Fireworks exploded over the Kremlin in Moscow amid glorious scenes across the capital.
In Turkey spectacular scenes were pictured over the Ortakoy mosque.
Egypt saw a man dressed in a Santa outfit selling toys to mark the occasion.
Fireworks exploded behind the quadriga of Berlin's landmark Brandenburg Gate.
In Greece, fireworks erupted over the ancient temple of the Parthenon on top of the Acropolis hill.
People took pictures of the fireworks erupting in the sky over the Arc de Triomphe during the New Year's celebrations on the Champs Elysees avenue, in Paris.
But in some places the festivities were marked by turmoil and political upheaval.
After more than six months of near-daily demonstrations, Hong Kong police fired tear gas a few minutes into 2020 as protesters marked the New Year with midnight countdown rallies and a massive march planned for January 1.
Before midnight on Tuesday, thousands gathered across the financial centre, including along the waterfront of Victoria Harbour and at nightlife hotspot Lan Kwai Fong.
Protesters at the harbour-front counted down, chanting "Ten, nine, liberate Hong Kong, revolution now," as they used their phones to form a sea of lights.
Smaller crowds of protesters in the Mong Kok district set fire to barricades, before riot police unleashed 2020's first volleys of tear gas in response.
In Paris, 250,000 to 300,000 people usually gather on the Champs-Elysees to welcome the New Year, but this year the turnout was marred by a transport strike that has spelt weeks of misery for commuters.
