The pledging conference comes mid-way through a three-day ceasefire which appeared to have brought calm to the capital Khartoum, after the failure of earlier truces to ensure secure aid corridors.
More than two months into the fighting, the United Nations is worried that the crisis could spill over and destabilize neighboring African states.
"The scale and speed of Sudan's descent into death and destruction is unprecedented," UN Secretary-General Guterres told the conference.
"Without strong international support, Sudan could quickly become a locus of lawlessness, radiating insecurity across the region."
Since April 15, the army, led by Abdel Fattah al-Burhan, has been battling the paramilitary Rapid Support Forces (RSF) commanded by his former deputy Mohamed Hamdan Dagalo, after the two fell out in a power struggle.
Hundreds of kilometers west of Khartoum, up to 1,100 have been killed in the West Darfur state capital El Geneina alone, according to the US State Department, blaming "primarily" the RSF.
A record 25 million people -- more than half Sudan's population -- are in need of aid, according to the UN.
The UN has two appeals for tackling the crisis -- the humanitarian response within Sudan, which needs $2.6 billion this year, and the regional refugee response, which needs $470 million.
However, both are less than 17 percent funded.
"The situation in Darfur and Khartoum is catastrophic," Guterres said. "Sudan was already grappling with a humanitarian crisis. This has now escalated into a catastrophe affecting more than half the country's people"
Qatar's prime minister told the conference there was "no military solution" to the conflict, as he pledged $50 million.
Sheikh Mohammed bin Abdulrahman bin Jassim Al Thani urged the warring parties to "put the aspirations of the Sudanese people in the forefront".
Germany doubled its existing donation to 200 million euros ($218 million), while the European Union pledged 190 million euros in humanitarian and development assistance.
Egypt's Foreign Minister Sameh Shoukry said the conflict risks a humanitarian crisis that could spill over the borders. He said the security and stability of Sudan "is our own stability and security".
UN refugees chief Filippo Grandi said he had seen for himself the "dire state" in which many Sudanese refugees were arriving in Egypt, and urged countries to keep their borders open.
UN humanitarian chief Martin Griffiths said the conflict was causing "unbearable suffering" which was also "gutting the economy and sending the prices of basic goods soaring".
"We are in a race against time to pre-position supplies before the onset of the rainy season," he added.
Indeed, with farm fields left fallow because of fuel and other shortages during the war, the UN's Food and Agriculture Organization (FAO) said earlier Monday that hunger was set to increase substantially as the country heads into the June-September lean season.
FAO wants to take advantage of the relatively calm conditions in rural Sudan and the current planting season to rapidly increase local food production, providing seeds, equipment and livestock.
The temporary ceasefire was a chance to end the "sea of suffering", he told the UN Human Rights Council.
Several Khartoum residents told AFP they heard no air strikes, artillery or other fighting on Monday, a rare respite for the war-weary suffering shortages of medical care, electricity, water and other essentials.
The UN, African Union and east African regional bloc IGAD, in a joint statement ahead of the donors' meeting, expressed particular concern about "the rapidly deteriorating situation in Darfur.
They said the conflict had taken on an ethnic dimension in Darfur, resulting in targeted attacks based on people's identities and subsequent displacement of communities".
With their 72-hour ceasefire both the RSF and army "agreed to allow the unimpeded movement and delivery of humanitarian assistance throughout the country", US and Saudi mediators said on Saturday.