Countries in Asia and the Pacific have been the first to welcome in 2011.
New Zealand's main city of Auckland became one of the first to see in the new year with onlookers packing the harbour to enjoy a huge fireworks display.
As the clock struck midnight, the city's 328 metre Sky Tower became the launch pad for a spectacular pyrotechnic show.
In Australia, crowds gathered in Sydney Harbour to watch what is hailed as the biggest New Year's Eve fireworks display.
Displays are also planned in many cities in Europe, including a musical and fireworks at the UK's London Eye big wheel - which is marking its 10th anniversary.