The United Nations, or UN, is an international organization established in 1945. The UN describes itself as a "global association of governments facilitating cooperation in international law, international security, economic development, and social equity." It was founded by 51 states. From its headquarters in New York City, the member countries of the UN and its specialized agencies give guidance and make decisions on substantive and administrative issues in regular meetings held throughout each year. The UN was founded at the conclusion of World War II by the victorious world powers, and the founders of the UN had high hopes that it would act to prevent conflicts between nations and make future wars impossible, by fostering an ideal of collective security. The organization's structure still reflects in some ways the circumstances of its founding; specifically, in addition to the rotating national members of the prominent United Nations Security Council, there are five permanent members with veto power — the United States of America, Russia, United Kingdom, France, and China.

The idea of the United Nations issuing its own stamps was first proposed by Argentina in 1947. An agreement with the United States postal authorities was reached in 1951 and it stipulated that the stamps be denominated in United States currency, and used only at UN Headquarters. The first United Nations stamps were issued in U.S. dollar denominations on United Nations Day, 24 October, in 1951. Similar postal agreements were reached with the Swiss and Austrian postal authorities. On 11 December 1968, an agreement between the United Nations and the Swiss Postal Telephone and Telegraph Enterprise enabled the Geneva office of UNPA to issue the first UN stamps in Swiss francs on 4 October 1969. A similar agreement with the Austrian government on 28 June 1979 enabled the Vienna office of UNPA to issue the first UN stamps in Austrian schillings on 24 August 1979.

Nowadays United Nations stamps are issued simultaneously at UN offices in New York, Geneva and Vienna. Each issue carries a related design theme, with different denominations for each office. The stamps are valid for postage when used on mail from the UN offices in New York, Geneva and Vienna: