The UN pleaded with the world to come to the rescue of Yemen, South Sudan, Somalia and northeast Nigeria.
"We stand at a critical point in history. Already at the beginning of the year we are facing the largest humanitarian crisis since the creation of the UN," UN humanitarian chief Stephen O'Brien said Friday.
"Now, more than 20 million people across four countries face starvation and famine. Without collective and coordinated global efforts, people will simply starve to death. Many more will suffer and die from disease."
The UN was founded in 1945.
Terror group stealing food
In Somalia, more than 6 million people are in need of food assistance -- more than half the population
Drought, impending famine and the presence of terrorist group Al-Shabaab have left the country and its people in a desperate situation.
"The situation is critical in Somalia. People are dying of hunger and there is no water," said Mogadishu resident Noor Ibrahim, who fled his home to seek help at a camp.
"Al-Shabaab blocks the roads, there is no access for food aid, the Shabaab steal food as well."
South Sudan, where a famine was recently declared, has more than 7.5 million people in need of assistance -- more than half of whom have been displaced, according to the UN.
In northeast Nigeria, "famine looms for over 120,000 people," the UN's World Food Programme
And in Yemen, more than 7 million people are severely food insecure, the UN said.
UN Secretary-General Antonio Guterres made a similar appeal this week, warning that the crisis facing Somalia has been "neglected" by the world.
"Let's not forget that each one of these people is an individual case of extreme suffering," he said.
"There is a moral obligation for us all to do everything we can to support these people."
Money is needed in Somalia -- and quickly. In addition to drought and famine, diseases, such as cholera and measles are beginning to spread.
Last week, Somali Prime Minister Hassan Ali Khaire announced that 110 people had died from starvation and drought-related illness.
Correction: A previous version of this article incorrectly listed the four countries the UN says face a famine risk. The countries are Somalia, South Sudan, Yemen and Nigeria.