More than four million Venezuelans have fled their country amid an economic and humanitarian crisis, UN agencies say.
The pace of people fleeing has "skyrocketed" since the end of 2015, with around one million leaving in the last seven months alone, they found.
The agencies said countries hosting the migrants and refugees were in "urgent need" of international support.
Venezuela's imploding economy has meant shortages of basic supplies, such as food and medicines, in recent years.
The crisis has deepened this year amid a bitter power struggle between the government and opposition.
The exodus means Venezuelans are now "one of the single largest population groups displaced from their country", the UN refugee agency (UNHCR) and International Organization for Migration (IOM) said in a joint statement on Friday.
The agencies said they calculated the four million figure using data from national immigration authorities and other sources.
They did not give an exact date for when the calculation began, but said some 3.3 million people had fled since the end of 2015.
A UNHCR spokesperson told the BBC that the real figure may be even higher due to the use of unofficial border crossings.
The agencies called for support to be given to countries hosting the Venezuelans.
"Latin American and Caribbean countries are doing their part to respond to this unprecedented crisis but they cannot be expected to continue doing it without international help," said Eduardo Stein, joint UNHCR-IOM special representative for Venezuelan refugees and migrants.
Latin American countries host the vast majority of Venezuelan migrants and refugees. According to UN figures, Colombia hosts the most at 1.3 million, followed by Peru with 768,000.
Countries in Central America and the Caribbean also host significant numbers of Venezuelans.
Under the government of Nicolás Maduro, the economy has collapsed and shortages of food and medicines have become widespread.
In parts of the oil-rich country, fuel has become scarce and drivers queue for days at petrol stations. There are also frequent blackouts.
The government says the shortages are caused by US sanctions. The opposition argues that they are the result of mismanagement and corruption by consecutive socialist governments.
Venezuela is engulfed in a political crisis with two rival politicians - Mr Maduro and National Assembly leader Juan Guaidó - claiming to be the country's legitimate leader.
Mr Guaidó declared himself interim president in January, arguing that Mr Maduro's re-election last year had been "illegitimate".
He has since been recognised by more than 50 countries, including Canada, the US and most in Latin America. But Mr Maduro retains the loyalty of most of the military and important allies such as China and Russia.
On 30 April, Mr Guaidó led a failed attempt to spark a military rebellion against Mr Maduro, which the latter said was part of a US-orchestrated coup.
Since then, close allies of Mr Guaidó have been arrested. While his parliamentary immunity has been lifted, he has so far not been jailed.
Representatives of the two sides have been holding talks in Norway but they ended without agreement last week.