Lochnaw Castle is a 16th-century tower house five miles from the town of Stranraer, in the historical county of Wigtownshire, Scotland.

The central square tower, five storeys high, formed part of the new castle.

Lochnaw Castle shows four periods of construction – a simple 16th-century keep, 17th- and 18th-century domestic dwellings, and a mansion-house, which was later demolished.

[1] An earlier, ruined castle stands on an island in the nearby Lochnaw Loch.

A royal castle, this was given to the Agnews in 1363, but was sacked by Archibald The Grim, 3rd Earl of Douglas in 1390, and subsequently dismantled.