An explosion at the Chernobyl Nuclear Power Plant in 1986 spread a radioactive cloud over large parts of the Soviet Union, now the territories of Belarus, Ukraine and the Russian Federation. Nearly 8.4 million people in the three countries were exposed to the radiation.

The Soviet Government acknowledged the need for international assistance only in 1990. That same year the General Assembly adopted resolution 45/190, calling for “international cooperation to address and mitigate the consequences at the Chernobyl nuclear power plant.” That was the start of the United Nations' involvement in the Chernobyl recovery. An Inter-Agency Task Force was established to coordinate the Chernobyl co-operation. In 1991 the UN created the Chernobyl Trust Fund - currently under the management of the Office for the Coordination of Humanitarian Affairs (OCHA). Since 1986, the UN family of organizations and major NGOs have launched more than 230 different research and assistance projects in the fields of health, nuclear safety, rehabilitation, environment, production of clean foods and information.

In 2002 the United Nations announced a shift in the Chernobyl strategy, with a new focus on a long-term developmental approach. UNDP and its regional offices in the three affected countries took the lead in the implementation of the new strategy. There is still a great deal of work that needs to be done in the affected region. To provide support to international, national and public programmes targeted at the sustainable development of these territories, in 2009 UN launched the International Chernobyl Research and Information Network (ICRIN)

On 8 December 2016 the United Nations General Assembly adopted a resolution designating 26 April as International Chernobyl Disaster Remembrance Day. The General Assembly recognized that, “three decades after the Chernobyl disaster, the still-persistent serious long-term consequences thereof, as well as the continuing related needs of the affected communities and territories,” and invited “all Member States, relevant agencies of the United Nations system and other international organizations, as well as civil society, to observe the day.”