Pamlico Sound is a large estuarine lagoon in North Carolina. The largest lagoon along the North American East Coast, it extends 80 mi (130 km) long and 15 to 20 miles wide. It is part of a large, interconnected network of similar lagoons that includes Albemarle Sound, Currituck Sound, Croatan Sound, Roanoke Sound, Pamlico Sound, Bogue Sound, Back Sound, and Core Sound known collectively as the Albemarle-Pamlico sound system. With over 3,000 sq. mi. (7,800 km2) of open water the combined estuary is second only in size to 4,479 sq mi (11,600 km2) Chesapeake Bay in the United States.

A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into coastal lagoons and atoll lagoons. They have also been identified as occurring on mixed-sand and gravel coastlines. There is an overlap between bodies of water classified as coastal lagoons and bodies of water classified as estuaries. Lagoons are common coastal features around many parts of the world.