The North Shore of Long Island is the area along the northern coast of New York's Long Island bordering Long Island Sound. Known for its extreme wealth and lavish estates, the North Shore exploded into affluence at the turn of the 20th century, earning it the nickname the Gold Coast. Historically, this term refers to the affluent coastline neighborhoods of the towns of North Hempstead and Oyster Bay in Nassau County and Huntington in Suffolk County. Some definitions may also include the parts of Smithtown that face the Sound. The region is also largely coextensive with the Gold Coast region of Long Island, though this region excludes Smithtown, as the easternmost Gold Coast mansion is the Geissler Estate, located just west of Indian Hills Country Club in the Fort Salonga section of Huntington.

Long Island Sound is a marine sound and tidal estuary of the Atlantic Ocean. It lies predominantly between the U.S. state of Connecticut to the north and Long Island in New York to the south. From west to east, the sound stretches 110 mi (180 km) from the East River and the Throgs Neck Bridge in New York City, along the North Shore of Long Island, to Block Island Sound. A mix of freshwater from tributaries, and saltwater from the Atlantic Ocean, Long Island Sound is 21 mi (34 km) at its widest point and varies in depth from 65 to 230 feet.