Sketrick Castle lies on Sketrick Island in Strangford Lough, south east of the town of Comber, in County Down, in Northern Ireland.
Local tradition has it that Sketrick Castle was built by the Vikings but an Anglo-Norman or even 15th century origin is more likely. The castle was first mentioned in The Annals of the Four Masters as being taken by a great army lead by the O'Neill into Clannaboy to assist MacQuillan in 1470. During the 16th century it was several times actively involved in warfare.
Sketrick Castle was built as a rectangular 4-storey tower house. It probably had 4 chambers at ground level, the largest with a vault and 2 brick-lined recesses, probably ovens. The central space may have been a boat bay and the small windowless room could have been a lock-up or treasury. The entrance in the eastern wall was protected by a murder-hole. A straight mural stairway rose to the left of the entrance and continued in the southern wall to the second floor level. A spiral stairway near the north east corner gave access to the upper levels.
The castle guarded the causeway to the west of the island which gave access to the island from the mainland. And in medieval times access to the island was through a narrow passage at the base of the tower. This passageway was blocked but has been restored in recent years.
In 1833 Sketrick Castle was described as a plain, stone building about 40 feet high, oblong in form and did not appear to have any flanking towers or outworks attached to it. The castle was not habitable then, being unroofed and open from the top to the ground. It stood fairly intact until 1896 when half of it collapsed during a storm.
In 1957 a small, stone, subterranean passage was discovered. It has lintels running eastwards under the bawn wall to a space with a corbel over a fresh water spring. The passage is less than 1 meter high and about 15 meters long.
At present the castle is freely accessible. A somewhat interesting castle on a nice location.