List of Connecticut counties:
- Fairfield County: one of four original counties created in Connecticut in 1666. Historic county seats: Bridgeport and Danbury.
- Hartford County: one of four original counties created in Connecticut in 1666. Historic county seat: Hartford.
- Litchfield County: formed in 1751 from parts of Fairfield County, Hartford County, and New Haven County. Historic county seats: New Milford and Winsted.
- Middlesex County: formed in 1785 from parts of Hartford County and New London County. Historic county seat: Middletown.
- New Haven County: one of four original counties created in Connecticut in 1666. Historic county seats: New Haven and Waterbury.
- New London County: one of four original counties created in Connecticut in 1666. Historic county seats: New London and Norwich.
- Tolland County: formed in 1785 from parts of Hartford County, and Windham County. Historic county seat: Tolland.
- Windham County: formed in 1726 from parts of Hartford County, and New London County. Historic county seats: Putnam and Willimantic.
