Thomaston is a town in Litchfield County, Connecticut, United States. The population was estimated to be 7,535 in 2019, down from 7,887 at the 2010 census but up from 7,503 at the 2000 census. The urban center of the town is the Thomaston census-designated place, with a population of 1,910 at the 2010 census.
The town, originally part of the town of Plymouth and referred to as "Plymouth Hollow", was first settled by Henry Cook ("the soldier in the wilderness", 1683–1750) around 1728. The town is known for clockmaking, which started in 1803, when Eli Terry established a factory in the town. Terry brought mass production to the clockmaking industry, helping to reduce the cost of clocks. He introduced and patented the shelf clock in 1814, which reduced the cost of a clock from $25 to $5. His clocks were sold throughout the United States.
The town was incorporated in its own right and under the name "Thomaston" in 1875. The name derives from Seth Thomas, the early clockmaker, who established a factory in town in 1812. The Seth Thomas clock factory building still exists; however, the clockmaking industry has long since left the state as well as the country.
Thomaston is in southeastern Litchfield County, bordered on the south by the city of Waterbury in New Haven County.