thumb|right|Vice-counties of Great Britain and the Isle of Man (Orkney and Shetland not shown)
thumb|Map showing detailed differences between Derbyshire vice-county (VC57) and the modern administrative county of [[Derbyshire, England]]
A vice-county (also spelled vice county)
Vice-counties are the "standard geographical area for county based [...] recording". They provide a stable basis for recording using similarly sized units, and, although National Grid-based reporting has grown in popularity, vice-counties remain a useful mapping boundary, employed in many regional surveys, especially county floras and national lists. This allows data collected over long periods of time to be compared easily. The vice-counties remain unchanged by subsequent local government reorganisations, allowing historical and modern data to be more accurately compared.
In 2002, to mark the 150th anniversary of the introduction of the Watsonian vice-county system, the NBN Trust commissioned the digitisation of the 112 vice-county boundaries for England, Scotland and Wales, based on 420 original one-inch to the mile maps annotated by Dandy in 1947, and held at the Natural History Museum, London. The resulting datafiles were much more detailed than anything readily available to recorders up to that point, and were made freely available (as a beta version). Intended for use with modern GIS and biological recording software, a final 'standard' version was released in 2008. Up until that point, county recorders only had general access to a set of two fold-out vice-county maps covering the entirety of Great Britain, published in 1969.
Vice-county systems
The vice-county system was first introduced by Hewett Cottrell Watson in the third volume of his Cybele Britannica published in 1852. He refined the system in later volumes. The geographical area that Watson called "Britain" consisted of the island of Great Britain with all of its offshore islands, plus the Isle of Man, but excluding the Channel Islands. This area was divided into 112 vice-counties with larger counties divided; for example, Devon into the vice-counties of North Devon and South Devon, and Yorkshire into five vice-counties. Each of these 112 vice-counties has a name and a number. Thus Vice-county 38, often abbreviated to "VC38", is called "Warwickshire". Other recording schemes regard the "British Isles" as including the Channel Islands. As they are not part of the 152 vice-county system, the Channel Islands may be added as an extra vice-county, making 153 in total, being indicated by letter codes such as "C" Less usually, each of the five separate islands may be treated as a vice-county, giving 157 vice-counties in total.
Alternative counts of vice-counties used in different recording schemes are shown in the table below.
{| class="wikitable" border="1"
|+ Alternative counts of vice-counties
! Count !! Originator !! Descriptions
|-
|style="text-align:center"| 112 || Watson || Great Britain (including the Isle of Man)
|-
|style="text-align:center"| 40 || Praeger || Ireland
|-
|style="text-align:center"| 0, 1 or 5 || || Channel Islands (Jersey, Guernsey, Alderney, Sark and Herm)
|- style="border-top:solid 2px black"
|style="text-align:center"| 152, 153 or 157 || || British Isles, (Great) Britain and Ireland
|}
The vice-counties of Britain alone may be described as "Watsonian vice-counties", or this term may be used for the combined vice-counties of Britain and Ireland, In all cases, the Channel Islands may be excluded
!VC!!Vice county!!County!!Province!!Jurisdiction
|-
| || South Kerry || Kerry || Munster || Republic of Ireland
|-
| || North Kerry || Kerry || Munster || Republic of Ireland
|-
| || West Cork || Cork || Munster || Republic of Ireland
|-
| || Mid-Cork || Cork || Munster || Republic of Ireland
|-
| || East Cork || Cork || Munster || Republic of Ireland
|-
| || Waterford || Waterford