Stranraer , town (1991 pop. 10,766), Dumfries and Galloway, SW Scotland, at the head of Loch Ryan. A fishing port, it has a prosperous trade with Northern Ireland. Food processing is an industry. Viscount Dundee occupied the 15th-century castle while suppressing Covenanters in Galloway in 1682. Northwest Castle was the home of the explorer John Ross.