Middletown is a city located in Middlesex County, Connecticut, along the Connecticut River, in the central part of the state, 16 miles (26 km) south of Hartford. In 1650, it was incorporated as a town under its original Indian name, Mattabeseck. It received its present name in 1653. Middletown was included within Hartford County upon its creation on May 10, 1666. In 1784, the central settlement was incorporated as a city distinct from the town. Both were included within newly formed Middlesex County in May 1785. In 1923, the City of Middletown was consolidated with the Town, making the city limits of the city quite extensive.

Originally a busy sailing port and then an industrial center, it is now largely residential with its downtown serving as a popular retail, dining, and entertainment district proximal to Wesleyan University. Middletown was the county seat of Middlesex County from its creation in 1785 until the elimination of county government in 1960. As of the 2010 census, the city had a total population of 47,648. Middletown, Connecticut is considered the southernmost city in the Hartford-Springfield Knowledge Corridor Metropolitan Region, which features a combined metro population of 1.9 million.

The land on the western bank of the Connecticut River where Middletown now lies was home to the Mattabesett Native Americans (also spelled Mattabesec, Mattabeseck, and Mattabesek); the area they inhabited—now Middletown and the surrounding area—was named after them. At the time the first European settlers arrtived in the region, the Mattabesetts were a part of the group of tribes in the Connecticut Valley, under a single chief named Sowheag.

Plans for the colonial settlement of "Mattabesett" were drawn up by the General Court in 1646; the first Europeans arrived from nearby Connecticut colonies in 1650. The Name Middletown was chosen because the site was approximate halfway between Windsor and Saybrook on the Great River. Life was not easy among these early colonial Puritans; clearing the land and building homes, and tending farms in the rocky soil of New England was a labor-intensive ordeal. Law, too, was often harsh among the Puritans; offenses legally punishable by death in the Connecticut colonies included, "witchcraft, blasphemy, cursing or smiting of parents, and incorrigible stubbornness of children."

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