The Thames River is a short river and tidal estuary in the U.S. state of Connecticut. It flows south for 15 mi. (25 km.) through eastern Connecticut from the junction of the Yantic and Shetucket Rivers at Norwich, to New London and Groton, which flank its mouth at the Long Island Sound.
Differing from its namesake, the River Thames in England, Connecticut's "Thames" is pronounced as it is written, to rhyme with "James," rather than as "temz" (as /θeɪmz/ rather than /tɛmz/), reflecting the pre-Hanoverian English pronunciation. (But see Thames#Origin of the name).
The river has provided important harbors since the mid-17th century when it was known as the Pequot River for the Pequot Indians who lived in the area. Other early names for the river have included Frisius, Great, Great River of Pequot, Little Fresh, Mohegan, New London, and Pequod.
The Harvard-Yale Boat Race is held annually in New London.