Portencross Castle is situated overlooking the Firth of Clyde near West Kilbride in Ayrshire.

The castle was constructed in three phases starting around 1360. It was the home of a branch of the Boyds.

The lands around Portencross were given to the Boyds of Kilmarnock by King Robert I as a reward for their help at the Battle of Bannockburn. A number of Royal Charters were signed at the castle and it had close links with King Robert II during that period.

After the 1600s, it was occupied by local fishermen. The roof was destroyed in a gale in January 1739. By the 20th century, the Adams of Auchenames owned the castle. It became a scheduled ancient monument in 1955.