Smerby Castle, also known as Island Muller Castle, is a ruined fortified house on a promontory known as Isla Muller, Kintyre, Argyll and Bute, Scotland, north of Campbeltown.

[1] The site is protected as a scheduled monument.

Angus MacDonald, 8th of Dunnyveg was kept as a prisoner in chains at Smerby Castle in 1598 after James MacDonald was sent to seek his fathers submission to King James V of Scotland.

Angus suffered burns after his Kintyre house Askomull was burnt down by his son James and was subsequently captured.

In a 1594 Bond by James "Macdonald" of Smerby, signed as M'Connall and a 1597 Bond by Sir James "MacDonald" of Knockrinsay also signed as M'Connall [3]