The Flatiron Building (or Fuller Building, as it was originally called) is located at 175 Fifth Avenue in the borough of Manhattan, New York City and is considered to be a groundbreaking skyscraper. Upon completion in 1902, it was one of the tallest buildings in the city and the only skyscraper north of 14th Street. The building sits on a triangular island-block formed by Fifth Avenue, Broadway and East 22nd Street, with 23rd Street grazing the triangle's northern (uptown) peak. As with numerous other wedge-shaped buildings, the name "Flatiron" derives from its resemblance to a cast-iron clothes iron.

The building anchors the south (downtown) end of Madison Square and the north (uptown) end of the Ladies' Mile Historic District. The neighborhood around it is called the Flatiron District after its signature building, which has become an icon of New York City. The building was designated a New York City landmark in 1966, was added to the National Register of Historic Places in 1979, and designated a National Historic Landmark in 1989.