"This emergency financing under the new Food Shock Window will help South Sudan address food insecurity, support social spending, and boost international reserves," the IMF said in a statement.
On Tuesday, the IMF put the number of people experiencing severe food insecurity at an estimated 8.3 million.
In early-November, United Nations agencies said up to 7.8 million people in South Sudan, two-third of the population, may face severe food shortages during next year's April-to-July lean season due to floods, drought and conflict.
"The combination of continued localized conflict, four consecutive years of severe flooding, and the rising price of staple commodities from Russia's war in Ukraine has increased the number of people experiencing severe food insecurity," it said.
South Sudan erupted into civil war shortly after getting independence from Sudan in 2011 and while a peace agreement signed four years ago is largely holding, the transitional government has been slow to unify various military factions.