Rothesay Castle is a ruined castle in Rothesay, the principal town on the Isle of Bute, in western Scotland. Located at NS086646, the castle has been described as "one of the most remarkable in Scotland" for its long history dating back to the beginning of the 13th century, and its unusual circular plan.
The castle comprises a huge curtain wall, strengthened by four round towers, together with a 16th century forework, the whole surrounded by a broad moat. Built by the Stewart family, it survived Norse attacks to become a royal residence. Though falling into ruin after the 17th century, the castle was repaired by the Marquees of Bute before passing into state care last century.
The castle was built either built by Alan, High Steward of Scotland, or by his son Walter Stewart. Alan was granted the lands of the Isle of Bute by William I in 1200. A wooden castle was constructed first, but the stone circular curtain wall was in place by the 1230s, when the castle was attacked and taken by Norsemen under Gillespec MacDougall (known as Uspak in Norse), grandson of Somerled. According to The Saga of Haakon Håkonsson, the Norsemen fought for three days to take the castle, breaking down part of the eastern wall by hewing the stone with their axes, and certainly the eastern wall shows signs of damage. This saga is the earliest recorded account of an assault on a Scottish castle. In 1263, Rothesay was taken again by the Norse under Haakon IV before the Battle of Largs although the Battle of Largs was indecisive, Haakon's campaign was unsuccessful, and effectively ended Norse influence in western Scotland.