Fairfield, county, southwestern Connecticut, U.S. It is bounded by Long Island Sound to the south, New York state to the west, and the Housatonic River to the east, and it includes several islands in the sound. Most of the county lies in an upland region forested with hardwoods, with only a narrow coastal plain running along the southern edge. Waterways other than the Housatonic are the Saugatuck, Pequonnock, Mill, and Norwalk rivers as well as Saugatuck, Easton, and Hemlock reservoirs and Lake Candlewood. Parklands include Paugussett and Pootatuck state forest reserves and Collis P. Huntington and American Shakespeare Theater state parks.

The Mahican (Mohican) and Wappinger Indians inhabited the region in the early 17th century. In 1637 colonists from the Thames River valley pursued the Pequot Indians to present-day Southport, defeating them in the Great Swamp Fight. Stratford and Fairfield, both founded in 1639, were among Connecticut’s first settlements. The county, formed in May 1666, was the site of several battles during the American Revolution. There is no county seat because county government in Connecticut was abolished in 1960.

The principal communities are Bridgeport, Stamford, Norwalk, Danbury, Greenwich, Fairfield, and Stratford. The University of Bridgeport (founded 1927) and Fairfield University (founded 1942) are two major schools. The county’s proximity to New York City makes it a popular residential and resort area as well as an attractive location for corporate headquarters. Some major economic activities are retail trade and manufacturing. Bridgeport, one of Connecticut’s leading industrial cities, produces transportation equipment, electrical goods, and machine tools. Area 626 square miles (1,621 square km). Pop. (2000) 882,567; (2010) 916,829.