Guilford is a town in New Haven County, Connecticut, United States, that borders Madison, Branford, North Branford and Durham, and is situated on I-95 and the coast. The population was 21,398 at the 2000 census. It was named one of the top 100 places to live in the United States by Money magazine in 2005.

First settled in 1639 after being purchased from Native American leader Wequash, Guilford is considered by some to have the third largest collection of historic homes in New England, with important buildings from the 17th, 18th, and 19th centuries There are five historic house museums, including Dudley Farm and the Henry Whitfield House (1639), the oldest dwelling house in Connecticut and the oldest stone house in North America. The Comfort Starr House (1645–46), is one of the oldest wooden framed private dwellings in Connecticut, and one of the few houses remaining of the original signers who settled Guilford.

According to the United States Census Bureau, the town has a total area of 49.7 square miles (129 km²), of which 47.0 square miles (122 km²) is land and 2.7 square miles (6.9 km² or 5.39%) is water.

Connecticut (ⁱ/kəˈnɛtɨkət/) is a state in the New England region of the northeastern United States. It is bordered by Rhode Island to the east, Massachusetts to the north, and the state of New York to the west and the south (with which it shares a water boundary in Long Island Sound).

Connecticut is named for the Connecticut River, the major U.S. river that approximately bisects the state. Its capital city is Hartford. Much of southern and western Connecticut (along with the majority of the state's population) is part of the New York metropolitan area; three of Connecticut's eight counties are statistically included in the New York City combined statistical area, the same area is widely referred to as the Tri-State area. Connecticut's center of population is in Cheshire, New Haven County, which is also located within the Tri-State area.

Connecticut is the 3rd least extensive, the 29th most populous, and 4th most densely populated of the 50 United States. Called the Constitution State, Nutmeg State, and "The Land of Steady Habits", Connecticut was influential in the development of the federal government of the United States.