In the British Isles, a county council is a council that governs a county.

The first county councils were introduced in the late 19th century in England and Wales, and the system was soon extended to Scotland and the island of Ireland. The areas they covered were termed administrative counties, and did not necessarily align with the traditional counties. The new system was a major modernisation, which reflected the increasing range of functions carried out by local government in late Victorian England.

County councils were responsible for more strategic services in a region, with smaller urban district councils and rural district councils responsible for other activities.

The writ of the county councils did not extend everywhere: county boroughs were independent of the council for the county in which they were geographically situated, and county borough councils exercised the functions of both county councils and district councils.

In England and Wales local government was reformed in 1974. County boroughs were abolished and all of the country (apart from Greater London) was placed in a two-tier arrangement with county councils and district councils.

Another reform in 1986 abolished the Greater London Council (which was similar but not identical to a county council) and the councils of the six metropolitan counties abolished. Their functions were transferred to the metropolitan boroughs.

In 1996 in Wales another local government reform replaced the two-tier system with an arrangement of unitary counties and county boroughs of Wales. There therefore continue several county councils.

The 1990s in England saw the reestablishment of county boroughs in all but name, as unitary authorities. As a result of this, a further county council, that of Berkshire, was abolished, whilst others saw their territory decrease. Most of these unitary authorities were boroughs or districts, but two, Rutland and Herefordshire, correspond to traditional counties, and so their councils are known as county councils.

In Scotland a major reform took place in 1975. This resulted in bodies identical in function and structure to the England and Welsh county councils; but called 'regional councils', because they covered regions instead of counties. In 1996 a further reorganisation saw the regions and districts replaced by 32 Unitary Council areas.

In Northern Ireland, county councils were abolished in 1973, along with urban and rural districts and county boroughs, and they were replaced by a consistent system of 26 districts.

In the Republic of Ireland, the county councils are still around in their original form, though they have taken on the powers of rural districts after they were abolished.

In the United States, most of the individual states have counties as a form of local government, usually with a county council in charge of it.