United Nations (UN) is an intergovernmental organization comprising most of the world countries, whose stated purposes are to maintain international peace and security, develop friendly relations among nations, achieve international cooperation, and serve as a centre for harmonizing the actions of nations. It is the world's largest international organization. The UN is headquartered in New York City (in the United States, but with certain extraterritorial privileges), and the organization has other offices in Geneva, Nairobi, Vienna, and The Hague, where the International Court of Justice is headquartered.
The UN was established after World War II with the aim of preventing future world wars, and succeeded the League of Nations, which was characterized as ineffective. On 25 April 1945, 50 nations met in San Francisco, California for a conference and started drafting the UN Charter, which was adopted on 25 June 1945. The charter took effect on 24 October 1945, when the UN began operations. The organization's objectives, as defined by its charter, include maintaining international peace and security, protecting human rights, delivering humanitarian aid, promoting sustainable development, and upholding international law. At its founding, the UN had 51 member states; as of 2023, it has 193 – almost all of the world's sovereign states.
The organization's mission to preserve world peace was complicated in its early decades due in part to Cold War tensions that existed between the United States and Soviet Union and their respective allies. Its mission has included the provision of primarily unarmed military observers and lightly armed troops charged with primarily monitoring, reporting and confidence-building roles. UN membership grew significantly following widespread decolonization in the 1960s. Since then, 80 former colonies have gained independence, including 11 trust territories that had been monitored by the Trusteeship Council. By the 1970s, the UN's budget for economic and social development programmes vastly exceeded its spending on peacekeeping. After the end of the Cold War in 1991, the UN shifted and expanded its field operations, undertaking a wide variety of complex tasks.
An international organization, also known as an intergovernmental organization or an international institution, is an organization that is established by a treaty, or is an instrument governed by international law and possessing its own legal personality, such as the United Nations, the World Health Organization, Save the Children International, and NATO. International organizations are composed of primarily member states, but may also include other entities, such as other international organizations, firms, and nongovernmental organizations. Additionally, entities (including states) may hold observer status. An alternative definition is that an international organization is a stable set of norms and rules meant to govern the behavior of states and other actors in the international system.
Notable UN bodies include the United Nations (UN) Educational, Scientific and Cultural Organization (UNESCO), World Health Organization (WHO), Bank for International Settlements (BIS), Council of Europe (COE), International Labour Organization (ILO), International Crimes Tribunal (ICT) and International Criminal Police Organization (INTERPOL), and International Court of Justice (ICJ).