Ardgillan Castle is a country house in Balbriggan, Fingal, Ireland. It is set in the 200-acre Ardgillan Demesne. Featuring castellated embellishments, the building overlooks Barnageera Beach, the Irish Sea and Balbriggan. The castle consists of two storeys over a basement, which extends under the south lawns. When occupied, the ground and first floors were the living accommodation while the west and east wings were servants quarters and estate offices.