Cromartyshire was one of the 34 traditional counties into which Scotland was divided. As an administrative area it was an extremely odd one. It comprised a series of nine exclaves scattered across the separate county of Ross-shire.
The core of the county comprised an area around Cromarty in the north of the Black Isle, which was the only burgh in the county and served as the county town. The largest exclave, however, extended inland from Ullapool on the west coast. The remaining exclaves forming the county included those around Portmahomack on the east coast and around Dundonnell and Little Loch Broom on the west coast. Another included Ben Wyvis.
This very peculiar county owed its origins to Sir George Mackenzie, Viscount Tarbat and 1st Earl of Cromartie. He owned estates across northern Scotland and in the 1680s and 1690s succeeded in having his estates brought under the control of the Sheriffdom of Cromarty, which he also controlled. In due course the Sheriffdom of Cromarty became the County of Cromartyshire.
A reorganisation of Scotland's counties in 1890 tidied up the map and removed various enclaves and exclaves in a number of parts of the country. The major change, however, was the reduction in the total number of counties from 34 to 33 by merging Cromartyshire and Ross-shire to form the single county of Ross and Cromarty with Dingwall as its county town.