The secretary-general of the United Nations (UNSG or just SG) is the head of the United Nations Secretariat, one of the six principal organs of the United Nations. The secretary-general serves as the chief administrative officer of the United Nations. The role of the United Nations Secretariat, and of the secretary-general in particular, is laid out by Chapter XV (Articles 97 to 101) of the United Nations Charter.

The Secretary-General is appointed by the General Assembly, on the recommendation of the Security Council. The Secretary-General's selection is therefore subject to the veto of any of the five permanent members of the Security Council. Although there is technically no limit to number of five-year terms a Secretary-General may serve, none so far has held office for more than two terms.

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