A county seat is an administrative center, seat of government, or capital city of a county or civil parish. The term is used in Canada, China, Romania, Taiwan and the United States. County towns have a similar function in the United Kingdom and Republic of Ireland, and historically in Jamaica.

In most of the United States, counties are the political subdivisions of a state. The city, town, or populated place that houses county government is known as the seat of its respective county. Generally, the county legislature, county courthouse, sheriff's department headquarters, hall of records, jail and correctional facility are located in the county seat, though some functions (such as highway maintenance, which usually requires a large garage for vehicles, along with asphalt and salt storage facilities) may also be located or conducted in other parts of the county, especially if it is geographically large.

A county seat is usually, but not always, an incorporated municipality. The exceptions include the county seats of counties that have no incorporated municipalities within their borders, such as Arlington County, Virginia (where the county seat is the entire county^[1]). Ellicott City, the county seat of Howard County, is the largest unincorporated county seat in the United States, followed by Towson, the county seat of Baltimore County, Maryland. Likewise, some county seats may not be incorporated in their own right, but are located within incorporated municipalities. For example, Cape May Court House, New Jersey, though unincorporated, is a section of Middle Township, an incorporated municipality. In some of the colonial states, county seats include or formerly included "Court House" as part of their name, (e.g. Spotsylvania Courthouse, Virginia).

In the Canadian provinces of Prince Edward Island, New Brunswick, and Nova Scotia, the term "shire town" is used in place of county seat.

County seats in Taiwan are the administrative centers of the counties. Currently there are 13 county seats in Taiwan, which are in the forms of county-administered city, urban township or rural township.

Most counties have only one county seat. However, some counties in Alabama, Arkansas, Georgia, Iowa, Kentucky, Massachusetts, Mississippi, Missouri, New Hampshire, New York, and Vermont have two or more county seats, usually located on opposite sides of the county. An example is Harrison County, Mississippi, which lists both Biloxi and Gulfport as county seats. The practice of multiple county seat towns dates from the days when travel was difficult. There have been few efforts to eliminate the two-seat arrangement, since a county seat is a source of pride (and jobs) for the towns involved.

There are 36 counties with multiple county seats (no more than two each) in 11 states:

In New England, the town, not the county, is the primary division of local government. Historically, counties in this region have served mainly as dividing lines for the states' judicial systems. Connecticut (since 1960) and Rhode Island have no county level of government and thus no county seats. In Vermont, Massachusetts,^[3] and Maine^[4] the county seats are legally designated shire towns. County government consists only of a Superior Court and Sheriff (as an officer of the court), both located in the respective shire town. Bennington County has two shire towns (Manchester for the North Shire, Bennington for the South Shire), but the Sheriff is located in Bennington. In Massachusetts, most government functions which would otherwise be performed by county governments in other states are performed by town or city governments (there are no unincorporated areas in the state; that is, all land area in the state is within either a town or a city). As such, Massachusetts has dissolved many of its county governments, and the state government now operates the registries of deeds and sheriff's offices in those counties.

In Virginia, a county seat may be an independent city surrounded by, but not part of, the county of which it is the administrative center; for example, Fairfax City is both the county seat of Fairfax County and is completely surrounded by Fairfax County, but the city is politically independent of the county.

Two counties in South Dakota (Oglala Lakota and Todd) have their county seat and government services centered in a neighboring county. Their county-level services are provided by Fall River County and Tripp County, respectively.^[5]

In Louisiana, which is divided into parishes rather than counties, county seats are referred to as parish seats.

Alaska is divided into boroughs rather than counties; the county seat in these case is referred to as the "borough seat"; this includes six consolidated city-borough governments (one of which is styled as a "municipality"). The Unorganized Borough, which covers 49% of Alaska's area, has no county seat or equivalent.

The state with the most counties is Texas, with 254, and the state with the fewest counties is Delaware, with 3.