The Dag Hammarskjöld Library is a library on the grounds of the headquarters of the United Nations, located in the Turtle Bay/East Midtown neighborhood of Manhattan in New York City. It is connected to the Secretariat and Conference buildings through ground level and underground corridors. It is named after Dag Hammarskjöld, the second Secretary-General of the United Nations. The library was founded in 1946, and the current library building was completed in 1961.

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.