The Flatiron Building was one of the tallest buildings in New York City upon its completion in 1902. The building, at 175 Fifth Avenue in the borough of Manhattan, sits on a triangular island block at 23rd Street, Fifth Avenue, and Broadway, anchoring the south (downtown) end of Madison Square. The neighborhood around the building is called the Flatiron District after its signature building.

The Flatiron Building was designed by Chicago's Daniel Burnham in the Beaux-Arts style. Like a classical Greek column, its limestone and glazed terra-cotta façade is separated into three parts horizontally. Since it was one of the first buildings to use a steel skeleton, the building could be constructed to 285 feet (87 m), which would have been very difficult with other construction methods of that time.

At the rounded tip, the triangular tower is only 6.5 feet (2 meters) wide. The 22-story building, with a height of 285 ft (87 meters), is often considered the oldest surviving skyscraper in Manhattan, though in fact the Park Row Building (1899) is both older and taller.

The Flatiron Building is the third building in the flatiron shape, with the first being the Gooderham Building of Toronto, built in 1892, and the second in Atlanta in 1897. Both of the earlier buildings are smaller than their New York counterpart.