41°37′01″N 71°18′59″W / 41.6170°N 71.3164°W
Prudence Island is the third-largest island in Narragansett Bay in the state of Rhode Island and part of the town of Portsmouth, Rhode Island, United States. It is located near the geographic center of the bay. It is defined by the United States Census Bureau as Block Group 3, Census Tract 401.03 of Newport County, Rhode Island. As of the 2010 census, the population was 278 people living on a land area of 14.43 km (5.57 sq mi).
Narragansett Bay is a bay and estuary on the north side of Rhode Island Sound covering 147 square miles (380 km), 120.5 square miles (312 km) of which is in Rhode Island. The bay forms New England's largest estuary, which functions as an expansive natural harbor and includes a small archipelago. Small parts of the bay extend into Massachusetts.
There are more than 30 islands in the bay; the three largest ones are Aquidneck Island, Conanicut Island, and Prudence Island. Bodies of water that are part of Narragansett Bay include the Sakonnet River, Mount Hope Bay, and the southern, tidal part of the Taunton River. The bay opens on Rhode Island Sound and the Atlantic Ocean; Block Island lies less than 20 miles (32 km) southwest of its opening.