Two islands in the Firth of Clyde, Scotland, between the island of Bute and the district of Cunninghame, Strathclyde region (until 1975 in the county of Bute), on the mainland. Great Cumbrae (4.5 sq mi (11.5 sq km)) is built of ancient sandstone and reaches 415 ft (126 m). It is well farmed and has the holiday resort of Millport.