At least 2.5 billion people have been affected by natural disasters over the past 10 years - an increase of 60% over the previous decade, the UN says.
Millions have been affected by the Indian Ocean tsunami
More than 478,000 people were killed by disasters such as earthquakes, floods and hurricanes, from 1994 to 2003.
The most vulnerable people are those living in developing nations, it says.
The figures come ahead of a world conference on reducing the damage caused by natural disasters, which will look at a tsunami warning system.
The five-day meeting in Kobe, Japan, begins on Tuesday - a day after the 10th anniversary of an earthquake which shook the city, killing more than 6,000 people.
The conference had been scheduled to take place before the devastating Indian Ocean earthquake and tsunami, which killed more than 158,000 people on 26 December 2004.
Floods and earthquakes are the deadliest natural disasters, accounting for more than half of the total casualties over the course of the decade, the UN says.
Asia is named as the continent most affected during the period, accounting for more than half the casualties and more than 90% of those injured, left homeless or needing emergency assistance.
Numbers worldwide peaked in 2002, with millions affected by floods in Asia, and drought in India, Ethiopia and Zimbabwe.
Thousands of government officials, experts and specialists from around the world are expected to attend the Kobe conference to discuss ways to reverse the growth in numbers of people affected by natural disasters.
They are expected to produce a plan for a tsunami warning system in the Indian Ocean and other measures to reduce the risk of natural disasters.
Ahead of the meeting, the UN's emergency relief chief, Jan Egeland, said he was convinced more attention should be given to disaster prevention and preparedness.
"We need to be more than a fire brigade," he was reported as saying.
The UK's international development minister has called on government officials at the conference to boost spending on risk reduction.
"Poorer countries have fewer resources to cope with disasters and so are more vulnerable," Gareth Thomas said, "yet measures are available now such as early warning systems that could save lives."