More than 300 days into Russia's botched invasion of Ukraine, about 7,000 civilians have been killed and 10,000 more injured, according to the Office of the UN High Commissioner for Human Rights.
About 16 million Ukrainians have fled their homes.
For those who remain, an 11:00 pm to 5:00 am curfew will be in place amid periodic blackouts and Russian missile barrages.
The latest Russian strikes on Saturday targeted several regions, including the capital Kiev, where at least one person was killed and several wounded, Ukrainian officials said.
While some Ukrainians will mark New Year with quiet candlelit prayers, others intend to party through the night in a collective show of resolve.
In past years, "people always stayed with us until three or four in the morning, so staying here for another hour or two will not be a problem", said Kyiv restaurateur Tetyana Mytrofanov.
There seems to be a dulled appetite for grand celebrations in Vladimir Putin's Russia.
Moscow has cancelled its traditional fireworks show after Mayor Sergei Sobyanin asked residents to vote on how to mark the occasion.
Muscovites such as Irina Shapovalova, a 51-year-old nursery worker, said their main wish for 2023 was for "a peaceful sky above our heads".
State-owned broadcaster VGTRK has promised to provide a "New Year's atmosphere, despite the changes in the country and the world".
Putin said in a New Year's address that "moral, historical rightness" is on Russia's side as the country faces international condemnation over the war.
As Russia's Far East regions rang in the New Year, the Russian leader delivered his traditional midnight speech standing among soldiers who fought in Ukraine, according to Russian news agencies.
The new year will kick off with a new leader in Brazil, where Luiz Inacio Lula da Silva takes the reins on Sunday following his razor-thin win in October polls.
However, China begins 2023 battling a surge in Covid infections after unwinding restrictions to contain the virus.
While vaccines have allowed life to return to semi-normal in most parts of the world, the virus is continuing to thwart China's attempts to move on.
Hospitals in the world's most populous nation have been overwhelmed by an explosion of cases following the decision to lift strict "zero-Covid" rules.
New Year's Eve parties are still planned in innumerable bars, theatres and malls.
But authorities in Shanghai have said there will be no formal activities on the city's famed Bund waterfront.
Chinese President Xi Jinping told the country in a televised New Year's Eve address that, despite the outbreak, "the light of hope is right in front of us".