The headquarters of the United Nations (UN) is on 17 to 18 acres of grounds in the Turtle Bay neighborhood of Midtown Manhattan in New York City. It borders First Avenue to the west, 42nd Street to the south, 48th Street to the north, and the East River to the east. Completed in 1952, the complex consists of several structures, including the Secretariat, Conference, and General Assembly buildings, and the Dag Hammarskjöld Library. The complex was designed by a board of architects led by Wallace Harrison and built by the architectural firm Harrison & Abramovitz, with final projects developed by Oscar Niemeyer and Le Corbusier. The term Turtle Bay is occasionally used as a metonym for the UN headquarters or for the United Nations as a whole.

Headquarters denotes the location where most, if not all, of the important functions of an organization are coordinated. In the United States, the corporate headquarters represents the entity at the center or the top of a corporation taking full responsibility for managing all business activities. In the United Kingdom, the term head office is most commonly used for the headquarters of large corporations. The intended benefit of headquarters is to carry out purposeful regulatory capacity. The term is also used regarding military organizations.