In Tokyo, a car ploughed into crowds celebrating New Year's Day in Tokyo early on Tuesday in a suspected terror attack, leaving eight people injured, including one who was unconscious.
As people around the world celebrated the start of a new year, a police spokesman said one suspect, in his 20s, had been detained and that he had described the incident as an "act of terror". The spokesman declined to elaborate.
The incident happened shortly after midnight local time in a popular tourist area of Harajuku, near Meiji Shrine, in central Tokyo.
"I can't believe it, this is a place I'm familiar with, so it's very shocking," said Tatsuhiro Yaegashi, a 27-year-old worker in the area.
Meanwhile, in New York's Times Square, throngs of soggy revellers greeted 2019 with fireworks and the drop of a sparkling crystal ball. Christina Aguilera performed in a snow-white dress and coat while partygoers danced in their rain ponchos.
Umbrellas were banned as part of the tight security plan, reflecting concern over the possibility of random attacks.
Many around the square spent nearly half the day in the chilly rain waiting for the ball drop but, despite the grim weather, some said they felt energised by the crowd and hopeful the new year would be better than 2018.
The square erupted with fireworks and cheers at the stroke of midnight. Many had donned plastic rain ponchos and sported colourful, oversized top hats handed out by organisers.
Injecting a sombre note into the festivities, the Times Square Alliance, the business association that organises the event, paid a special tribute to freedom of the press, after a year in which journalists came under attack around the world, including in the United States.
In a new-year interview with Fox News, President Donald Trump predicted that Democrats lining up to run against him will be counted as the losers of 2018, while Americans benefiting from his policies are the winners.
Trump listed tax cuts, job growth and a strong military as boons for Americans.
"But I only - I'm really more interested in the winners, and the winners are the people of the United States," Trump said.
Rio de Janeiro's Copacabana beach hosted more than two million people who rang in the new year with a dip in the ocean and a 14-minute fireworks display only hours before far- right politician Jair Bolsonaro will be sworn in as president.
In London, Britons ushered in the new year with the familiar chimes of Big Ben just two weeks before parliament is back at the tortuous task of trying to work out how to exist the European Union without destroying either the economy, or relations with Ireland.
Paris was heavily patrolled by police and revellers subject to bag searches, a ban on alcohol and traffic restrictions after anti-government protesters from the yellow vest movement issued calls on social media for "festive" demonstrations on the Champs-Elysees. It did not deter thousands from turning up for the fireworks atop the Arc de Triomphe, however.
Berlin also endured heavy security with revellers banned from taking fireworks, bottles or large bags into the fenced-off party zone. By midnight, Berlin police reported fewer incidents than in previous years.
In the Vatican City, Pope Francis rounded out the most problematic year of his papacy with prayers before the Vatican's giant sand sculpture Nativity scene, and a couple of key resignations from his staff.
The United Arab Emirates returned to a traditional fireworks show at Dubai's Burj Khalifa, the world's tallest building, after last year's somewhat anticlimactic LED lightshow that ran down the facade of the 828-meter-tall (2,716-foot-tall) tower.
Hundreds of people in Thailand travelled to Takien Temple in a suburb of Bangkok to lie inside coffins in a ritual participants believe helps rid them of bad luck and allows them to be born again for a fresh start.
But dozens were injured in the Philippines when many set off powerful firecrackers as part of wild and sometimes fatal merrymaking. The tradition stems from a Chinese-influenced belief that noise drives away evil and misfortune.
Kiribati was was the first in the world to welcome the new year, greeting 2019 with muted celebrations after spending 2018 on the front line of the battle against climate change, where rising oceans have turned fresh water sources brackish, imperilling communities and raising doubts the nation will exist at the next New Year. Former President Anote Tong said the only future for Kiribati may be mass migration.
Reuters, Washington Post, AP