From Sydney to Dubai, revelers welcomed 2014 with extravagant fireworks displays, while London celebrated by spraying clouds of fruit-flavored mist and San Francisco and Seattle planned large outdoor festivities.
In New York, hordes of people, many decked out in cartoonish hats, waving balloons and ringing bells, faced frigid temperatures and heightened security in Times Square for the annual New Year's Eve street party.
Crowds heard musical performances by Miley Cyrus and Melissa Etheridge, who performed the Beatles song "Imagine," and then saw the ritualistic dropping of the New Year's Eve ball, which was followed by music and a sea of confetti that filled Midtown Manhattan.
US Supreme Court Justice and New York native Sonia Sotomayor helped to usher in 2014 by pushing a button to signal the lowering of the 11,875-pound, crystal-encrusted ball and leading a 60-second countdown.
Other performers included hip-hop artists Macklemore & Ryan Lewis. In outer space, Nasa astronauts prepared a message from crew members on board the International Space Station orbiting the globe, sending greetings to the Times Square crowd.
The celebrations were not without violence, however. Several hours before the ball dropped in Times Square, two men were slashed at a nearby bus station in what a Port Authority spokesman said was a dispute over tickets. Both victims were taken to a local hospital for treatment of non-life threatening wounds.
There was no crystal ball for Brasstown, in the mountains of North Carolina. At midnight it held its 20th New Year's Eve "possum drop" - in which a caged opossum is displayed in a Plexiglas container for spectators.
"If New York can drop a ball... then we can lower the opossum," organizers explained on their website. The event got a last-minute go-ahead after a judge refused a plea by animal-rights group People for the Ethical Treatment of Animals to stop the event.
Across the northern United States, partygoers braced for snow and freezing temperatures, said Roger Edwards, a meteorologist with the National Weather Service.
"The biggest story is the extreme cold," Edwards said, pointing to lows that could reach 40 degrees below zero Fahrenheit (-40 degrees Celsius) on Tuesday night in North Dakota, Minnesota, and Wisconsin.
Parts of northern New England were to face temperatures near or below zero and snowfall was expected to fall across the broader Midwest, stretching from Iowa to Pennsylvania.
Chicago was offering free rides on trains and buses from 10pm to 4am to ensure revelers make it home safely. Residents in Vincennes, Indiana, didn't let the cold air stop their fifth annual Watermelon Drop and Fireworks display in which 14 of the hefty fruits fell in a nod to the area's agricultural roots.
The event followed a performance by the melon-smashing comedian Gallagher, local media reported. In Nashville, Tenn., revelers saw the "Music Note Drop" backed up by musical performances, including by Hank Williams Jr., and fireworks.
Not everyone took to the streets, however. President Barack Obama celebrated a low-key New Year's Eve with his family at vacation rental in Hawaii.
In San Francisco, one of the last major cities in the world to see the clock strike midnight, some 200,000 people were expected to gather on the waterfront for a fireworks display illuminating the city's world-famous Golden Gate Bridge.
In Seattle, big crowds were expected for a fireworks display launched from the Pacific Northwest city's iconic Space Needle.
In other parts of the world, festivities were well under way or finished. At midnight in Sydney, Australia, a massive fireworks display lit up the sky around the city's famed Harbor Bridge and Opera House. New Year's organizers in Dubai attempted to break the Guinness World Record for largest fireworks display.
In London, edible banana confetti and strawberry mist rained from the sky as a fireworks display along the River Thames lit up Big Ben and other landmarks.
Across the United States, 2014 will also usher in political changes and the official start of a slate of new laws.
At midnight, New York City's next mayor, Bill de Blasio, was sworn in at a private ceremony at his home in Brooklyn, succeeding Mayor Michael Bloomberg, who is leaving office after 12 years.
Former President Bill Clinton will deliver the oath of office for de Blasio at a formal inauguration ceremony on Wednesday at City Hall.
Americans who have signed up for new health-care coverage under President Barack Obama's Affordable Care Act are expected to begin receiving benefits on January 1.
Before ushering in 2014, Sotomayor, the US Supreme Court Justice, granted Roman Catholic-affiliated groups a temporary exemption from a part of the Obamacare healthcare law that requires employers to provide insurance policies covering contraception.
In Colorado, a new law will allow state residents to buy an ounce of marijuana at a time from specially regulated retailers. Possession, cultivation and private personal consumption of marijuana by adults has already been legal in Colorado for more than a year.
"It will be like people waiting in line for tickets to a Pink Floyd concert," said Justin Jones, 39, owner of Dank Colorado in Denver, who has run a medical marijuana shop for four years and now has a recreational pot license.