A county town is a county's administrative centre in the United Kingdom or Ireland. County towns are usually the location of administrative or judicial functions, or established over time as the de facto main town of a county. The concept of a county town eventually became detached from its original meaning of where the county administration is based (see County halls below). In fact, many county towns are no longer part of "their" administrative county. For example, Nottingham is administered by a unitary authority entirely separate from the rest of Nottinghamshire. Many county towns are in fact cities, but all are referred to as county towns irrespective of whether city status is held or not.

Als Kreisstadt wird eine Stadt bezeichnet, in der ein Landkreis seinen Sitz hat. Dort befindet sich das Landratsamt oder die Kreisverwaltung. Es gibt auch Städte, die Sitz eines Landkreises sind, ohne zum Gebiet des Landkreises zu gehören, z. B. Heilbronn, Sitz des Landkreises Heilbronn.