The Thames River is a short river and tidal estuary in the U.S. state of Connecticut. It flows south for through eastern Connecticut from the junction of the Yantic and Shetucket rivers at Norwich, to New London and Groton, which flank its mouth at Long Island Sound. The Thames River watershed includes a number of smaller basins and the 80-mile-long Quinebaug River, which rises in southern Massachusetts and joins the Shetucket River about four miles northeast of Norwich.