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 Connecticut coast. The town is part of the South Central Connecticut Planning Region. The population was 22,073 at the 2020 census.

New Haven County is a county in the south central part of the U.S. state of Connecticut. As of the 2020 census, the population was 864,835, making it the third-most populous county in Connecticut. Two of the state's top 5 largest cities, New Haven (3rd) and Waterbury (5th), are part of New Haven County.