The counties of Ireland (Irish: contaetha na hÉireann; Ulster-Scots: coonties o Airlann) are sub-national divisions that have been, and in some cases continue to be, used to geographically demarcate areas of local government. These land divisions were formed following the Norman invasion of Ireland in imitation of the counties then in use as units of local government in the Kingdom of England. The older term “shire” was historically equivalent to “county”. The principal function of the county was to impose royal control in the areas of taxation, security and the administration of justice at the local level. Cambro-Norman control was initially limited to the southeastern parts of Ireland; a further four centuries elapsed before the entire island was shired. At the same time, the now obsolete concept of county corporate elevated a small number of towns and cities to a status which was deemed to be no less important than the existing counties in which they lay. This double control mechanism of 32 counties plus 10 counties corporate remained unchanged for a little over two centuries until the early 19th century, since when counties have been adapted and in some cases divided by legislation to meet new administrative and political requirements.
The powers exercised by the Cambro-Norman barons and the Old English nobility waned over time. New offices of political control came to be established at a county level. In the Republic of Ireland, some counties have been split resulting in the creation of new counties. Along with certain defined cities, counties still form the basis for the demarcation of areas of local government in the Republic of Ireland. Currently, there are 26 county level, 3 city level and 2 city and county entities – the modern equivalent of counties corporate – that are used to demarcate areas of local government in the Republic.
In Northern Ireland, counties are no longer used for local government; districts are instead used. Upon the partition of Ireland in 1921, the county became one of the basic land divisions employed, along with county boroughs.