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 and as of 2005 it consists of 191 member states, including virtually all internationally-recognized independent nations. 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 organization is structurally divided into administrative bodies, including the UN General Assembly, UN Security Council, UN Economic and Social Council, UN Trusteeship Council, UN Secretariat, and the International Court of Justice, as well as counterpart bodies dealing with the governance of all other UN system agencies, for example, the WHO and UNICEF. The organization's most visible public figure is the Secretary-General.

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 (which replaced the Soviet Union), United Kingdom, France, and the People's Republic of China (which replaced the Republic of China).