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.