The United Nations (UN; French: Organisation des Nations Unies, ONU) is the world's largest, foremost, and most prominent international organization. The stated aims of the United Nations include promoting and facilitating cooperation in international law, international security, economic development, social progress, human rights, civil rights, civil liberties, political freedoms, democracy, and the achievement of lasting world peace. The UN was founded in 1945 after World War II to replace the League of Nations, to stop wars between countries, and to provide a platform for dialogue. It contains multiple subsidiary organizations to carry out its missions.

At its founding, the UN had 51 member states; as of 2011, there are 193. From its offices around the world, the UN and its specialized agencies decide on substantive and administrative issues in regular meetings held throughout the year. The organization has six principal organs: the General Assembly (the main deliberative assembly); the Security Council (for deciding certain resolutions for peace and security); the Economic and Social Council (for assisting in promoting international economic and social cooperation and development); the Secretariat (for providing studies, information, and facilities needed by the UN); the International Court of Justice (the primary judicial organ); and the United Nations Trusteeship Council (which is currently inactive). Other prominent UN System agencies include the World Health Organization (WHO), the World Food Programme (WFP) and United Nations Children's Fund (UNICEF). The UN's most prominent position is that of the office of Secretary-General which has been held by Ban Ki-moon of South Korea since 2007.