Quonochontaug (KWAHN-uh-kon-tog[1]) is a coastal lagoon in the towns of Charlestown and Westerly, both in Washington County, Rhode Island, United States.

In contrast to the other ponds, however, much of its western barrier beach remains in a protected, undeveloped state even though it is privately owned.

Water quality in past years has been very good because the pond is relatively deep, well flushed by the tides, and development has been limited.

Like all the ponds, Quonochontaug is an important nursery for winter flounder, young striped bass, blue fish, and tautog.

In the past few years, development pressures have increased dramatically, even though the watershed area is relatively small and a large portion of it is wet, red maple swamps.