Cromwell is a town in Middlesex County, Connecticut, United States, located within the Lower Connecticut River Valley Planning Region. The population was 14,225 at the 2020 census.

Middlesex County is a county in the south central part of the U.S. state of Connecticut. As of the 2020 census, the population was 164,245. The county was created in May 1785 from portions of Hartford County and New London County.