Damsay is an island in the Orkney archipelago in Scotland. It is approximately 18 hectares (0.07 sq mi) in extent and rises to only 11 metres (36 ft) above sea level. It is situated in the Bay of Firth north of the Orkney Mainland near Finstown. Nearby is the smaller islet of Holm of Grimbister.
It is now uninhabited, but at one time a Norse hall stood there, and it was the scene of the killing of Earl Erlend Haraldsson by Earls Rögnvald Kali Kolsson and Harald Maddadsson in 1154. Erlend celebrated after returning to the island for Christmas and retired to his ship the worse for drink on the night of 21st December. Despite being warned of an attack by Sweyn Asleifsson and the presence of a full moon his men were taken by surprise by the attack by his co-rulers and Erlend was killed. Later a small nunnery was built on the island leading to a legend that no frogs or toads (or possibly rats and mice) could live there. It is also said that unmarried woman who became pregnant would go there to pray at an abandoned shrine to St Mary.