Thomaston is a town in Litchfield County, Connecticut, United States. The population was 7,503 at the 2000 census.
The town, originally part of Plymouth, Connecticut, and referred to as 'Plymouth Hollow' was first settled in the early 18th century. The town is known for clock making, which started in 1803, when Eli Terry established a factory in the town. Terry brought mass production to the clock making industry, helping to reduce the cost of clocks. He introduced and patented the shelf clock in 1814, which reduced the cost of a clock form $25 to $5. His clocks were sold throughout the US. It 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 clock making industry has long since left the state and eventually the country.
According to the United States Census Bureau, the town has a total size of 12.2 square miles (31.7 km²). 12.0 square miles (31.1 km²) of it is land and 0.2 square miles (0.6 km²) of it (1.80%) is water.