Kilmarnock Castle, called after 1700 Dean Castle, was for over 400 years the primary seat of the Boyd family. The castle is located about a mile north of the town of Kilmarnock, in the county of Ayre, in western Scotland. It is now open to the public as "Dean Castle Country Park," belonging to the Kilmarnock and Louden District Council. The name "Kilmarnock" is an ancient one describing the location of "Marnock's Church." Marnock was a noted early Irish missionary to that area of Scotland. The name "Dean" is an old Scottish term for a wooded glen and is a common place name today.
The earliest part of the castle is a fourteenth century keep, constructed not long after the lands of Kilmarnock and West Kilbride were given by King Robert the Bruce to Sir Robert Boyd as a reward for his faithful service in thick and thin during Bruce's fight for Scottish independence against Edward I and Edward II of England. A fifteenth century addition, the "palace" and its adjoining tower, were built during a period of Boyd ascendancy while Lord Boyd was the guardian of James III.
The main castle buildings burned in 1735, reputedly caused by a careless maid. After the fire the Boyds vacated the site and moved into town. After Lord William Boyd was executed in 1746 for supporting the Stewart cause, the castle was sold. It remained in ruins until being acquired about 1900 by the eighth Lord Howard de Walden, who "restored" the property over a period of thirty years. His son, the ninth Lord, donated the castle in 1976. The grounds were purchased by the District Council in 1977. The Country Park has been open since 1980.