New York City is located at the center of the BosWash megalopolis, 218 miles (350 km) driving distance from Boston and 220 miles (353 km) from Washington, D.C. The city's total area is 468.9 square miles (1,214.4 km²), of which 35.31% is water.[8] The city is situated on the three major islands of Manhattan, Staten Island, and western Long Island. The Bronx is the only borough that is part of the mainland United States.

New York City's significance as a trading city results from the natural harbor formed by Upper New York Bay, which is surrounded by Manhattan, Brooklyn, Staten Island, and the coast of New Jersey. It is sheltered from the Atlantic Ocean by the Narrows between Brooklyn and Staten Island in Lower New York Bay.

The Hudson River flows from the Hudson Valley into New York Bay, becoming a tidal estuary that separates the Bronx and Manhattan from New Jersey. The East River, actually a tidal strait, stretches from the Long Island Sound to New York Bay, separating the Bronx and Manhattan from Long Island. The Harlem River, another tidal strait between the East and Hudson Rivers, separates Manhattan from the Bronx.

The city's land has been altered considerably by human intervention, with substantial land reclamation along the waterfronts since Dutch colonial times. Reclamation is most notable in Lower Manhattan with modern developments like Battery Park City. Much of the natural variations in topography have been evened out, particularly in Manhattan. One possible meaning for "Manhattan" is "island of hills"; in fact, the island was quite hilly before European settlement