Colchester is a town in New London County, Connecticut, United States. The town is part of the Southeastern Connecticut Planning Region. The population was 15,555 at the 2020 census. In 2010 Colchester became the first town in Connecticut, and the 36th in the country, to be certified with the National Wildlife Federation as a Community Wildlife Habitat. The villages of Westchester and North Westchester are located within Colchester.