Ross-shire, or the County of Ross, was one of the 34 traditional counties into which Scotland was divided for administrative purposes. It extended from the east coast around Dingwall, the county town, to the mountainous west coast: and beyond, for it also included the Isle of Lewis in the Western Isles. Within its large area, Ross-shire contained nine enclaves which together formed the separate county of Cromartyshire, and it also had an enclave of the county of Nairnshire.
For the most part, Ross-shire was based on the traditional area of Ross. This had been one of the medieval mormaerdoms of Scotland at a time when the Norse and the Scots struggled for control of what is now northern Scotland. It later became an earldom that was fought over between the Lords of the Isles and the Stewart Kings of Scotland.
Still later it became a sheriffdom, and in the late 1600s it lost the areas owned by Sir George Mackenzie, Viscount Tarbat and 1st Earl of Cromartie, to his Sheriffdom of Cromarty. When the Sheriffdom of Ross became the County of Ross, or Ross-shire, the slightly chaotic layout remained. Ross-shire was often divided for descriptive purposes into Wester Ross and Easter Ross, with the dividing line between them vague, but approximately following the watershed. Both Wester Ross and Easter Ross survive as descriptive terms in common use into the modern era.
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.