Duart Castle, or Caisteal Dhubhairt in Scottish Gaelic, is a castle on the Isle of Mull, beside the Sound of Mull off the west coast of Scotland, within the council area of Argyll and Bute. The castle dates back to the 13th century and is the seat of Clan MacLean. One source states that the castle was "brought back from ruin in 1911". The regimental colours of the WW1 Canadian Expeditionary Force 236th Battalion, CEF are laid up in the Great Hall.

Castles are buildings that combine fortifications and residence, and many were built within the borders of modern Scotland. They arrived in Scotland with the introduction of feudalism in the twelfth century. Initially these were wooden motte-and-bailey constructions, but many were replaced by stone castles with a high curtain wall. During the Wars of Independence, Robert the Bruce pursued a policy of castle slighting. In the Late Middle Ages, new castles were built, some on a grander scale as "livery and maintenance" castles that could support a large garrison. Gunpowder weaponry led to the use of gun ports, platforms to mount guns and walls adapted to resist bombardment.