territorial trusteeship, system of UN control for territories that were not self-governing. It replaced the mandates of the League of Nations. Provided for under chapters 12 and 13 of the Charter of the United Nations, the trusteeship system was intended to promote the welfare of the native inhabitants and to advance them toward self-government. Trust territories were created out of former mandate territories of the League of Nations (with the exception of South West Africa, which remained under mandate until it achieved independence as Namibia in 1990) and former possessions of the Axis powers. Other dependent territories (colonies) remained outside the trusteeship system but came under the jurisdiction of chapter 11 of the Charter of the United Nations, obligating members responsible for dependencies to promote the welfare of their inhabitants.

The trusteeship system was supervised by the UN Trusteeship Council, members of the United Nations administering trust territories and an equal number of other member nations, including all permanent members of the Security Council not administering such territories. Each territory was governed by the provisions of a trusteeship agreement. Agreements covering nonstrategic areas were approved by the General Assembly and strategic areas were approved by the Security Council. Unlike territories under mandate, trusteeship territories could be fortified. The powers of the administering state included full legislative, administrative, and judicial authority and, in certain cases, the right to treat the territory as if it were part of the administering state. Each year the Trusteeship Council submitted to the responsible state a detailed questionnaire concerning each territory, with special emphasis on measures taken to increase self-government and educational opportunities. The council considered petitions from inhabitants of the territories and periodically made inspection tours. It met at least once a year and by majority vote (not subject to veto) adopted recommendations.

In 1949 the General Assembly, by virtue of the League of Nations mandate over Palestine, declared Jerusalem a trust territory under the administration of the whole United Nations. Because of the opposition of Israel and Jordan, the two occupying states, the implementation of this recommendation had to be postponed indefinitely. With the independence in 1994 of Palau (in free association with the United States), the self-governing status of all territories was established and the trusteeship agreements for those territories terminated. Of the earlier trusteeships, Italian Somaliland joined British Somaliland, becoming Somalia (1960); British Togoland joined Ghana (1956), and French Togoland became Togo (1960); French Cameroons became Cameroon (1960), joined by the southern British Cameroons (1961); and the northern British Cameroons joined Nigeria (1961). Tanganyika (now part of Tanzania) gained its independence in 1961, Samoa in 1962 (as Western Samoa, 1962–97), and Ruanda-Urundi became the states Rwanda and Burundi in 1962. Nauru became independent in 1968, New Guinea joined with Papua to become Papua New Guinea in 1975, and the Pacific Islands territory (Palau excepted) achieved commonwealth status (Northern Mariana Islands) or a independence under a compact of free association (Marshall Islands and the Federated States of Micronesia) with the United States in 1986.

See J. N. Murray, Jr., The United Nations Trusteeship System (1957); C. E. Toussaint, The Trusteeship System of the United Nations (1957); A. G. Mezerik, ed., Colonialism and the United Nations (1964).