Revelers around the globe are bidding farewell to a decade that will be remembered for the rise of social media, the Arab Spring, the #MeToo movement and, of course, President Donald Trump.
A look at how the world is ushering in 2020:
Revelers as well as pro-democracy protesters flocked to sites across Hong Kong to usher in 2020.
The semi-autonomous Chinese city has toned down New Year's celebrations amid the monthslong demonstrations. The protests have repeatedly sparked pitched battles with police and have taken their toll on Hong Kong's nightlife and travel industries.
A fireworks display that traditionally lights up famed Victoria Harbor was canceled amid safety concerns, while some roads were closed and barriers set up in the Lan Kwai Fong nightlife district to control crowds.
Russians began the world's longest continuous New Year's Eve with fireworks and a message from President Vladimir Putin urging them to work together in the coming year.
Putin made the call in a short speech broadcast on television just before the stroke of midnight in each of Russia's 11 time zones. The recorded message was followed by an image of the Kremlin Clock and the sound of its chimes. State TV showed footage of extensive festive fireworks in cities of the Far East.
But one holiday tradition was missing in Moscow this year - a picturesque layer of snow. The Russian capital has had an unusually warm December and temperatures in central Moscow as midnight approached were just above freezing.
More than a million people descended on a hazy Sydney Harbour and surrounding areas to ring in of the new year despite the ongoing wildfire crisis ravaging New South Wales, Australia's most populous state.
The 9 p.m. fireworks over Sydney's iconic landmarks was briefly delayed due to strong winds, but revelers clearly enjoyed themselves in a desperately needed tonic for the state.
New South Wales has born the brunt of the wildfire damage, which has razed more than 1,000 homes nationwide and killed 12 people in the past few months.
New Zealand's major cities greeted the new year with fireworks as the nation appeared happy to be done with a year of challenges, both natural and man-made.
On March 15, a lone gunman identified killed 51 people and wounded dozens at two mosques in the South Island city of Christchurch. In December, an eruption of volcanic White Island off the east coast of the North Island killed at least 19 tourists and tour guides.
In Samoa, New Year's Eve was more somber than usual. While fireworks erupted at midnight from Mount Vaea, overlooking the capital, Apia, the end of the year was a time of sadness and remembrance.
A measles epidemic in late 2019 claimed 81 lives, mostly children under 5.
More than 5,600 measles cases were recorded in the nation of just under 200,000. With the epidemic now contained, the Samoa Observer newspaper named as its Person of the Year health workers who fought the outbreak.
Londoners were making their way to the banks of the River Thames to jostle for position to watch a spectacular fireworks display launched from the London Eye and barges near Parliament.
The familiar chimes of London's Big Ben clock tower were to ring in the new year, even though they have been silent for most of 2019 because of extensive restoration work.
To the north, the multi-day Hogmanay New Year's celebrations in Edinburgh began Monday night with a torchlight parade through the streets of the Scottish capital.
Security was tight in both cities and elsewhere in Britain following a recent extremist attack on London Bridge that claimed two lives. Police arrested five men on suspicion of terrorism offenses Monday but said the arrests were not related to the London Bridge attack or to New Year's Eve celebrations.
Thousands of revelers gathered at Cape Town's Waterfront area to ring in the new year with music, dancing and fireworks in front of the city's iconic Table Mountain.
In past years, residents of Johannesburg's poor Hillbrow neighborhood would celebrate the New Year by tossing furniture, appliances and even refrigerators from the balconies of high-rise apartment buildings. Police have issued stern warnings, and it appears the dangerous tradition has declined.
In a somber statement, President Cyril Ramaphosa said "while our economy created jobs, these have not been nearly enough to stop the rise in unemployment or the deepening of poverty."
South African singer Yvonne Chaka Chaka was deported from Uganda, where she was to perform at a New Year's Eve event. Ugandan police cited visa issues, but Ugandan media reported it was because she had voiced support for Ugandan pop star Bobi Wine, the most potent opposition challenger to President Yoweri Museveni.
Pope Francis delighted tourists and Romans in St. Peter's Square on Tuesday night when he took a stroll to admire the Nativity scene. Shouts of "Pope! Pope!" and "Happy New Year!" resounded as families rushed to catch a glimpse of him or thrust out their infant in hopes he would pat their heads or pinch their cheeks.
One woman grabbed the pope's hand and pulled him toward her to shake it. Francis, 83, exclaimed and then struck the woman's hand twice to free his hand.
At a New Year's Eve Vespers service in St. Peter's Basilica, Francis urged people to practice more solidarity and to "build bridges, not walls." Since becoming pontiff in 2013, Francis has preached openness - a reform-minded agenda that has irritated a small but vocal group of ultra-conservatives in the church.
UNITED ARAB EMIRATES
For nearly 10 minutes, fireworks will light the sky over Dubai's Burj Khalifa, the world's tallest building, as hundreds of thousands gather downtown to watch the spectacular display.
The New Year's Eve display at the 828-meter-tall (2,716-foot-tall) skyscraper is just one of seven different fireworks shows across the emirate. Tourists, especially from Europe and Russia, flock to the sunny beaches of Dubai at this time of year to escape the cold, dark winter.
To keep the massive crowds safe, police have created walkways around the Burj Khalifa tower for male-only groups to separate them from families and women.
Dubai this year will be hosting Expo 2020, a world fair that brings the most cutting-edge and futuristic technologies.
People flocked to temples and shrines in Japan, offering incense with their prayers to celebrate the passing of a year and the the first New Year's of the Reiwa era.
Under Japan's old-style calendar, linked to emperors' rules, Reiwa started in May, after Emperor Akihito stepped down and his son Naruhito became emperor. Although Reiwa is entering its second year with 2020, Jan. 1 still marks Reiwa's first New Year's, the most important holiday in Japan.
Stalls at Zojoji Temple in Tokyo sold sweet rice wine, fried noodles and candied apples, as well as little amulets in the shape of mice, the zodiac animal for 2020. Since the Year of the Mouse starts off the Asian zodiac, it's associated with starting anew.
Tokyo will host the 2020 Summer Olympics, an event that is creating much anticipation for the entire nation.
Tens of thousands of revelers in Indonesia's capital of Jakarta were soaked by torrential rains as they waited for New Year's Eve fireworks while others in the country were wary of an active volcano.
Festive events along coastal areas near the Sunda Strait were dampened by a possible larger eruption of Anak Krakatau, an island volcano that erupted last year just ahead of Christmas Day, triggering a tsunami that killed more than 430 people.
The country's volcanology agency has warned locals and tourists to stay 2 kilometers (1.3 miles) from the volcano's crater following an eruption Tuesday that blasted ash and debris up to 2,000 meters (6,560 feet) into the air.
Thousands of South Koreans filled cold downtown streets in Seoul ahead of a traditional bell-tolling ceremony near City Hall to send off an exhausting 2019 highlighted by political scandals, decaying job markets and crumbling diplomacy with North Korea.
Dignitaries ringing the old Bosingak bell at midnight included South Korean Major League Baseball pitcher Hyun-Jin Ryu and Pengsoo, a giant penguin character with a gruff voice and blunt personality that emerged as one of the country's biggest TV stars in 2019.
Hundreds of thousands of revelers are expected to ring in the New Year in front of the Brandenburg Gate in Berlin.
Several German cities including Munich and Hamburg have banned private fireworks amid concerns about the danger and environmental impacts from the increasingly powerful fireworks. A recent poll by the Forsa research institute found 59% of Germans would support a ban on private fireworks in city centers, while 37% were opposed.
A joyful crowd of Parisians and tourists walked, biked and used scooters to reach the Champs-Elysees for the new year celebrations, in a city with almost no public transport amid massive strikes.
Revelers were converging toward the famous avenue to watch a light show at the Arc de Triomphe, followed by a fireworks display at midnight.
Paris police set up a security perimeter around the Champs-Elysees area with a ban on alcohol and traffic restrictions.
All metro lines in the French capital were closed except for two automatic lines, and only a few night buses were running, as Tuesday marked the 27th consecutive day of transport strikes against President Emmanuel Macron's plans to overhaul the French pension system.
A Chinese dance performance, punctuated with red and gold pyrotechnics, will usher in a host of stars at Times Square's six-hour New Year's Eve extravaganza.
The throng of revelers in the heart of Manhattan will get to see rap-pop star Post Malone, K-pop group BTS, country singer Sam Hunt and singer-songwriter Alanis Morissette during the big street party.
While giddiness will likely prevail at the televised event, some important global issues will be driven home, as well.
High school science teachers and students, spotlighting efforts to combat climate change, will press the button that begins the famous 60-second ball drop and countdown to next year.
Then comes the 3,000 pounds (1,360 kilograms) of confetti, accompanied by more pyrotechnics.