U Thant (ōō thänt), 1909–74, Burmese diplomat, secretary-general of the United Nations (1962–72). Educated at University College, Yangon, he later held positions in education, the press, and broadcasting. He was with the Burmese ministry of information (1949–57) and served as chairman of the Burmese delegation to the United Nations from 1947. In 1953 he was appointed Burma's permanent representative to the United Nations.
Thant succeeded Dag Hammarskjöld as acting secretary-general of the United Nations in 1961 and was elected secretary-general in 1962. In the early years of his tenure, he was deeply involved in the settlement of major international disputes, including the transfer of Netherlands New Guinea (now Papua and West Papua prov.) to Indonesia (1962); the removal of Soviet missiles from Cuba (1962); the resolution of the civil war in the Congo in 1963; the establishment of a peacekeeping force on Cyprus (1964); and the achievement of a cease-fire in the 1965 India-Pakistan War.
Elected to a second term in 1966, U Thant had less success in dealing with the major crises of this later period, which included the Vietnam War, the Middle East crisis, and another India-Pakistan War (1971), among others. This declining role in international peacekeeping was offset by a greatly increased UN involvement in the economic and social development of the Third World countries, which by that time made up a large majority of the United Nations. U Thant was never able to solve the chronic problem of financing UN operations.
In 1972, after declining another term, he was succeeded as secretary-general by Kurt Waldheim. He wrote several books, including Cities and Their Stories (1930), The League of Nations School Book (1932), Towards a New Education (1946), and a History of Postwar Burma (3 vol., 1961).
See a selection of his writings and speeches in Portfolio for Peace (1968); study by J. Bingham (1966).