Rossdhu Castle is located on the grounds of Loch Lomond Golf Club in Luss, Argyll and Bute, Scotland. The course occupies land previously held by Clan Colquhoun and includes the clan’s seat of Rossdhu Mansion as its clubhouse.
While Clan Colquhoun had occupied the site of the present club since ancient times, the medieval Rossdhu Castle was constructed by Sir John Colquhoun in 1457 along with the private chapel of St. Mary of Rossdhu when his lands were consolidated into the free Barony of Luss. Rossdhu is derived from the Scottish Gaelic ’ros dubh’, meaning the ’Black Headland’. Rossdhu Castle was ruined in a fire after the construction of Rossdhu Mansion. The ruins of the castle can be seen from the 18th green.