Earn, Loch, lake, 7 mi (11.2 km) long and 1 mi (1.6 km) wide, Perth and Kinross and Stirling, central Scotland. Ardvorlich House, on its shore, is the Darlinvarach of Sir Walter Scott's Legend of Montrose. Earn River (46 mi/74 km long), the lake's outlet, flows eastward through Strathearn past Comrie, Crieff, and Bridge of Earn into the Firth of Tay.