Arran (ârˈən) [key], island (1981 pop. 4,725), 165 sq mi (427 sq km), North Ayshire, W Scotland, in the Firth of Clyde. It is largely granitic and is wild and rocky; it rises to 2,866 ft (874 m). Its scenery and its hunting and fishing have made it a resort. Brodick is the chief town. Robert I hid on Arran (1306–7) and launched his invasion of the mainland from Arran.