Under Article 97 of the Charter of the United Nations, the Secretary-General is appointed as the Organization's chief administrative officer by the General Assembly upon the recommendation of the Security Council.

The current Secretary-General, as of 1 January 2017, is Mr. António Guterres (Portugal). His predecessors are: Ban Ki-moon (Korea) who served from January 2007 to December 2016; Kofi Annan (Ghana) who held office from January 1997 to December 2006; Boutros Boutros-Ghali (Egypt), who held office from January 1992 to December 1996; Javier Pèrez de Cuèllar (Peru), who served from January 1982 to December 1991; Kurt Waldheim (Austria), who held office from January 1972 to December 1981; U Thant (Burma, now Myanmar), who served from November 1961, when he was appointed acting Secretary-General (he was formally appointed Secretary-General in November 1962) to December 1971; Dag Hammarskjöld (Sweden), who served from April 1953 until his death in a plane crash in September 1961; and Trygve Lie (Norway), who held office from February 1946 to his resignation in November 1952.

Archives of all former Secretaries-General are available for consultation.