Castle Douglas is a town in Dumfries and Galloway, Scotland. It lies in the lieutenancy area of Kirkcudbrightshire, in the eastern part of Galloway, between the towns of Dalbeattie and Gatehouse of Fleet. It is in the ecclesiastical parish of Kelton.

Dumfries and Galloway is one of the 32 unitary council areas of Scotland, located in the western part of the Southern Uplands. It is bordered by East Ayrshire, South Ayrshire, and South Lanarkshire to the north; Scottish Borders to the north-east; the English ceremonial county of Cumbria, the Solway Firth, and the Irish Sea to the south, and the North Channel to the west. The administrative centre and largest settlement is the town of Dumfries. The second largest town is Stranraer, located 76 miles (122 km) to the west of Dumfries on the North Channel coast.