Former Scottish county in the south west of Scotland, washed on the west by the Firth of Clyde and the North Channel. Its greatest length was 78 miles and its greatest width was 28 miles. The chief towns were Ayr, Kilmarnock, Girvan, Maybole, Dalry, Kilwinning, Beith, Irvine, Stewarton, Cumnock, Ardrossan, Saltcoats, Troon, Mauchline, Galston, Newmilns, Kilbirnie, and Largs.

Following the Scottish local government reorganisation of 1974 Ayrshire was absorbed into Strathclyde Region and broken into four districts; Cunninghame (which also included the Islands of Arran, Great Cumbrae, and Little Cumbrae, from Buteshire), Kilmarnock and Loudon, Kyle and Carrick, and Cumnock and Doone Valley.

The name Ayrshire was resurrected following the second Scottish local government reorganisation, in 1996, and the abolition of Strathclyde and its districts. The new North Ayrshire council, headquartered in Irvine, administers the same geographic area as the former Cunninghame district. Similarly Kilmarnock and Loudon and Cumnock and Doune Valley became East Ayrshire, administered from Kilmarnock, and Kyle and Carrick became South Ayrshire, administered from Ayr.