Watertown is a town in Litchfield County, Connecticut, United States. The population was 22,514 at the 2010 census, up from 21,661 at the 2000 census. The ZIP codes for Watertown are 06795 (for most of the town) and 06779 (for the Oakville section). It is a suburb of Waterbury. The urban center of the town is the Watertown census-designated place, with a population of 3,574 at the 2010 census.
Colonization of the area today called Watertown began around 1657. In that time, the colony was called "Mattatock", though it had several variations in spelling through the years. The land where Watertown is now located, having originally belonged to Mattatock, officially changed its name to Watterbury (now Waterbury) by record on March 20, 1695, by consensus of a council. The original Colony of Mattatuck, which became Watterbury, then Waterbury in name, comprised a much greater land area than Waterbury does today. Thomas Judd and other families were among the first investors to buy the land as a group. The Town of Watertown was officially incorporated in 1780.
Watertown is in southeastern Litchfield County and is bordered to the southeast by the city of Waterbury in New Haven County.