Watertown is a town in Litchfield County, Connecticut, United States. The town is part of the Naugatuck Valley Planning Region. The population was 22,105 at the 2020 census. The ZIP Codes for Watertown are 06795 and 06779. It is a suburb of Waterbury. The urban center of the town is the Watertown census-designated place, with a population of 3,938 at the 2020 census.