Middletown is a city in Middlesex County, Connecticut, United States. Located along the Connecticut River, in the central part of the state, it is 16 miles south of Hartford. Middletown is the largest city in the Lower Connecticut River Valley Planning Region. In 1650, it was incorporated by English settlers as a town under its original Native American name, Mattabeseck, after the local Wangunk village of the same name. They were among many tribes along the Atlantic coast who spoke Algonquian languages. The colonists renamed the settlement in 1653.

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.