Caithness (Scottish Gaelic: Gallaibh) is a registration county, lieutenancy area and historic local government area of Scotland. The name was used also for the earldom of Caithness and the Caithness constituency of the Parliament of the United Kingdom (1708 to 1918). Boundaries are not identical in all contexts, but the Caithness area is now entirely within the Highland council area. In 2007 the Highland Council, which is now the local government authority, created the Caithness ward management area, which has boundaries similar to those of the historic local government area.
Caithness originally formed part of the shire or sheriffdom of Inverness, but gradually gained independence: in 1455 the Earl of Caithness gained a grant of the justiciary and sheriffdom of the area from the Sheriff of Inverness. In 1503 an act of the Parliament of Scotland confirmed the separate jurisdiction, with Dornoch and Wick named as burghs in which the sheriff of Caithness was to hold courts. The area of the sheriffdom was declared to be identical to that of the Diocese of Caithness. The Sheriff of Inverness still retained power over important legal cases, however until 1641. In that year parliament declared Wick the head burgh of the shire of Caithness and the Earl of Caithness became the heritable sheriff.