Charlestown is a census-designated place (CDP) in Washington County, Rhode Island, United States, comprising the main village in the town of Charlestown and additional land extending to the east into the town of South Kingstown.

[3] Charlestown is in southern Washington County, on the north side of Ninigret Pond, a tidal lagoon connected to Block Island Sound.

The village of Charlestown is in the northwestern part of the CDP, at the northern head of Ninigret Pond.

The CDP continues east into South Kingstown, on the north side of Green Hill Pond.

U.S. Route 1 forms the northern edge of the Charlestown CDP; the highway leads northeast 10 miles (16 km) to Narragansett and west 11 miles (18 km) to Westerly.