UN humanitarian chief Stephen O'Brien said that more than 20 million people faced the threat of starvation and famine in Yemen, Somalia, South Sudan and Nigeria, Censor.NET reports citing BBC.
Unicef has already warned 1.4 million children could starve to death this year.
Mr. O'Brien said $4.4 billion was needed by July to avert disaster. The UN had only received $90 million so far in 2017, despite generous pledges.
"We stand at a critical point in history," Mr. O'Brien told the Security Council on Friday. "Already at the beginning of the year we are facing the largest humanitarian crisis since the creation of the United Nations."
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.
It is thought a child dies every 10 minutes in Yemen from a preventable disease, while half-a-million children under five are suffering from severe acute malnutrition.
UN agencies say 100,000 people are facing starvation in South Sudan, while a further million are classified as being on the brink of famine.
The UN has described the unfolding disaster in north-eastern Nigeria as the "greatest crisis on the continent" - the full extent of which has only been revealed as extremist militant group Boko Haram is pushed back.
The last time a famine was declared in Somalia - just six years ago - nearly 260,000 people died.