Portincross Castle, also Portencross Castle, is a ruined castle in the Scottish town of Port Cross in the Unitary Authority North Ayrshire. In 1971 the building was added to the Scottish lists of monuments in the highest monument category A. Furthermore, the ruin is classified as a Scheduled Monument.
In 1306 came the lands in the possession of Robert Boyd of Kilmarnock and thus the clan Boyd, who used it until 1737. Portincross Castle was built during the 14th century and probably revised several times in the following centuries. In 1739, the building stood empty and is described as ruinous.
The ruin is located on the southern shore of the Firth of Clyde opposite the island of Little Cumbrae. It represents a remarkable building along the coastline dar. direct east is the village of Port Cross. The building has an L -shaped floor plan. It is unusual that the wing is not attached to the side but at the end of the elongated defensive tower. There are two entrance portals on the ground floor and the first floor. In these two floors are vaulted halls. Unusually for a building of this size, two kitchen areas are available.