Classiebawn Castle is a country house built for the 3rd Viscount Palmerston (1784–1865) on what was formerly a 4,000-hectare (10,000-acre) estate on the Mullaghmore Peninsula near the village of Cliffoney, County Sligo, Ireland.

The building was designed in the Baronial style by Dublin architect James Rawson Carroll, and is constructed from a yellow-brown sandstone brought by sea from County Donegal.

The land, which once belonged to the O'Connor Sligo family, was confiscated by the English Parliament to compensate the people who put down an Irish rebellion.

Around 4,000 hectares (10,000 acres) of land on which Classiebawn now stands was granted to Sir John Temple (1600–1677), Master of the Rolls in Ireland.

It was this Lord Palmerston who commissioned the building of the current Classiebawn Castle and the harbour at Mullaghmore.