Mattabesset was a region and settlement once occupied by Algonquian language-speaking Native Americans called the Wangunk, along the Connecticut River. The Mattabesset River reaches the Connecticut River near Middletown, Connecticut. European settler colonists established Middletown on the part of the region on the west side of the river, and a succession of settlements on the east side of the river, including Chatham and Middle Haddam, became East Hampton, Connecticut.