Cairnbulg Castle is a z-plan castle situated in Cairnbulg, Aberdeenshire, Scotland.
It was described by W. Douglas Simpson as one of the nine castles of the Knuckle, referring to the rocky headland of north-east Aberdeenshire.
Originally known as Philorth Castle it was built in the early 14th century, destroyed in the winter of 1308–1309 in the Wars of Independence, and re-built by the Fraser family in 1380.
Subsequently, a courtyard and outbuildings were added to the main tower.
It is now open to the public by appointment only..