Ardencaple Castle, also known as Ardincaple Castle, and sometimes referred to as Ardencaple Castle Light, is a listed building, situated about 1 statute mile (1.6 km) from Helensburgh, Argyll and Bute, Scotland.[3] Today, all that remains of the castle is a tower, perched on the edge of a plateau, looking down on a flat tract of land between it and the shore of the Firth of Clyde.[4] The original castle was thought to have been built sometime in the 12th century,[5] and part of the remains of the original castle were said to have existed in the 19th century.[2] Today, that sole remaining tower is used as a navigational aid for shipping on the Firth of Clyde. Because of its use as a lighthouse the tower has been called Ardencaple Castle Light.[6]