Lowther Castle is a crenellated country house in the historic county of Westmorland, which now under the current unitary authority of Westmorland and Furness, in the ceremonial county of Cumbria, England. The estate has belonged to the Lowther family, latterly the Earls of Lonsdale, since the Middle Ages. It is a fully managed ruin, open to visits by the public to the shell of the castle and some of the gardens since 2011.