Kisimul Castle is a medieval castle built on a small, rocky islet in an enclosed sea loch near what is now the town of Castlebay, Barra. It was probably built during the 15^th century by Gilleonan MacNeil, first Lord of Barra which was a title granted to him in 1427 by Alexander MacDonald, 9^th Lord of the Isles. The castle consists of a 3 storey tower house and an irregular curtain wall which takes the shape of the island. Various other buildings are found inside the wall including a freshwater well, and there is evidence of a slipway for the MacNeil galley, crew quarters and fish traps on the shore to the south of the castle.

The castle takes its name from the Gaelic, Caisteal Chiosmull, which means ‘castle of the rock of the small bay’. It is surrounded by the sea and the views of Barra from the curtain wall are splendid. Legend has it that the MacNeils came to Barra in 1039 and made the islet the clan MacNeil stronghold although there is little evidence of these earlier buildings as they would be beneath the present castle. However, an archaeological survey found pottery and a flint blade which showed that man used the islet well before the MacNeils.

The MacNeils played their part in Scottish history being present at Bannockburn, Worcester, Killiecrankie and the Jacobite Rising of 1715. The castle was besieged several times during the clan wars but was never captured. It is ironic that the castle was abandoned and fell in to disrepair with stone used as ballast for fishing boats when the Island of Barra was sold to repay clan debts in 1839. It was purchased in 1937 by Robert MacNeil, 45^th clan chief who completed the rebuilding of the castle to return it become the hereditary seat of the clan. In 2001 the castle was leased to Historic Scotland (now Historic Environment Scotland) for an annual sum of £1 and a bottle of whisky