Danielson is a borough in the town of Killingly in Windham County, Connecticut, United States. The population was 4,051 at the 2010 census. The borough has a total area of 1.2 square miles (3.1 km2 ), of which 1.1 square miles (2.8 km2 ) is land and 0.1 square miles (0.26 km2 Danielson was originally named "Danielsonville" for Gen. James Danielson, the builder of the first house in the settlement. It was renamed Danielson in 1895.
