Buchanan Castle is a ruined country house in Stirlingshire, Scotland, located 1mi west of the village of Drymen. The house was commissioned by James Graham, 4th Duke of Montrose and built in 1852-1858 as a home for the Montrose family, serving as such until 1925. It was built as a replacement for Buchanan Auld House, which is located 0.5mi to the northwest but was destroyed in a fire in 1852. The old house and surrounding lands had been the property of the Clan Buchanan but passed to the Clan Graham in the late 17th century. The roof of the building was removed in 1954 and the condition of the house has since deteriorated, but it remains the seat of the Clan Graham.