Ellon Castle is a scheduled monument within the town of Ellon, Aberdeenshire. Only ruins survive of the 16th-century structure that may incorporate sections from the 15th century together with 18th-century renovations. The ruins form a focal point in a formal 6-acre (2.4 ha) garden planted in 1745; an older Category A listed sundial dating from c. 1700 forms the centrepiece to the garden.