The Great Dismal Swamp is a large swamp in the Coastal Plain Region of southeastern Virginia and northeastern North Carolina, between Norfolk, Virginia, and Elizabeth City, North Carolina. It is located in parts of the southern Virginia independent cities of Chesapeake and Suffolk and northern North Carolina counties of Gates, Pasquotank, and Camden. Some estimates place the size of the original swamp at over one million acres (4,000 km²), stretching from Norfolk, Virginia to Edenton, North Carolina.

Lake Drummond, a 3,100-acre (13 km²) natural lake, is located in the heart of the swamp. The lake, a remarkably circular body of water, is one of only two natural lakes in Virginia. Along the Great Dismal Swamp's eastern edge runs the Dismal Swamp Canal, completed in 1805.

The Great Dismal Swamp National Wildlife Refuge was created in 1973 when the Union Camp Corporation of Franklin, Virginia, donated 49,100 acres (199 km²) of land after centuries of logging and other human activities devastated the swamp's ecosystems. The refuge was officially established through the Dismal Swamp Act of 1974, and today consists of over 112,000 acres (450 km²) of forested wetlands. Outside the boundaries of the refuge, the state of North Carolina has preserved and protected additional portions of the swamp through the establishment of the Dismal Swamp State Park. The park protects 22 square miles (57 km²) of forested wetland.

A 45,611-acre (184.58 km²) remnant of the original swamp was declared a National Natural Landmark in 1973, in recognition of its unique combination of geological and ecological features.