is located in New London County, Connecticut, in the state's southeastern corner. It includes the borough of Stonington, the villages of Pawcatuck, Lords Point, Wequetequock, the eastern half of the village of Mystic (the other half being in the town of Groton), and Old Mystic. The population was 17,906 at the 2000 census.
According to the United States Census Bureau, the town has a total area of 50.0 square miles (129.6 km²), of which, 38.7 square miles (100.2 km²) of it is land and 11.4 square miles (29.4 km²) of it (22.68%) is water.
In the waters off Stonington, the states of New York, Connecticut and Rhode Island come together at a single point.