The counties of the United Kingdom are subnational divisions of the United Kingdom, used for the purposes of administrative, geographical and political demarcation. By the Middle Agescounties had become established as a unit of local government, at least in England. By the early 17th century all of England, Wales, Scotland and Ireland had been divided into counties. The older term "shire" was historically equivalent to "county". In Scotland shire was the only term used until after the Act of Union 1707.
Since the early 19th century, counties have been adapted to meet new administrative and political requirements, and the word "county" (often with a qualifier) has been used in different senses for different purposes. In some areas of England and Wales, counties are still used to perform the functions of modern local government, while in other parts of the United Kingdom they have been replaced with alternative, unitary, systems; which are considered 'county level' authorities.
Today, in addition to local government counties, every part of the United Kingdom lies within what is known as one of the historic counties; which have formed geographic and cultural units since the Middle Ages.
Most ceremonial counties correspond to a metropolitan or non-metropolitan county of the same name, but often with reduced boundaries. The current arrangement is the result of incremental reform; from 1974 to 1996 the metropolitan and non-metropolitan counties corresponded directly with the ceremonial counties. From 1889 to 1974 areas with county councils were known as administrative counties and ceremonial counties were defined separately.
The six historic counties of Northern Ireland are no longer in use for administrative purposes. Combined with the boroughs of Belfast and Derry, the counties do serve for organisational purposes within government, and often with private businesses and sporting clubs.
The 1889 legislation created county councils, turned each civil county (with one exception) into a contiguous area (without separate fragments) and adjusted boundaries where civil parishes straddled county boundaries, or had fragments in more than one county. The counties of Ross and Cromarty were merged to form Ross and Cromarty.
One region and various districts, created in 1975, had areas similar to those of earlier counties, and various council areas, created in 1996, are also similar. Two of the three islands areas—Orkney and Shetland—have boundaries identical to those of earlier counties.