The League of Nations was the first worldwide intergovernmental organisation whose principal mission was to maintain world peace. It was founded on 10 January 1920 by the Paris Peace Conference that ended the First World War. The main organization ceased operations on 18 April 1946 when many of its components were relocated into the new United Nations. As the template for modern global governance, the League profoundly shaped the modern world.

An international organization, also known as an intergovernmental organization or an international institution, is an organization that is established by a treaty or other type of instrument governed by international law and possesses its own legal personality, such as the United Nations, the World Health Organization, International Union for Conservation of Nature, 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 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.