New London is a seaport city and a port of entry on the northeast coast of the United States, located at the outlet of the Thames River in New London County, Connecticut. The city is part of the Southeastern Connecticut Planning Region.

The Thames River is a short river and tidal estuary in the state of Connecticut. It flows south for 15 miles (24 km) through eastern Connecticut from the junction of the Yantic River and Shetucket River at Norwich, Connecticut, to New London and Groton, Connecticut, which flank its mouth at Long Island Sound. The Thames River watershed includes a number of smaller basins and the 80-mile (130 km) long Quinebaug River, which rises in southern Massachusetts and joins the Shetucket River about four miles northeast of Norwich.