Killingworth is a town in Middlesex County, Connecticut, United States. The town's name can easily be confused with another Connecticut town, Killingly; or a Vermont ski area, Killington. The population was 6,018 at the 2000 census. Killingworth was established from the area called Hammonasset, taken from the local Native American tribe of the same name. The area originally incorporated the town of Clinton, which were separated along ecclesiastical borders. Part of New London County prior to May 1785, Killingworth was then included in the newly formed Middlesex County, where it remains today. It was named after Kenilworth, England in honor of one of the first settlers. Kenilworth's name was more similar to "Killingworth" during the American colonial period, and over time the pronunciation and spelling drifted towards the modern one. Coincidentally, there is a town and village in England called Killingworth and Killingworth Village in the county of Tyne and Wear, which do not seem to have any connection with Killingworth, Connecticut.