Derwent Island House is an 18th-century Italianate house situated on Derwent Island, Derwent Water, Keswick, Cumbria, and in the ownership of the National Trust. It is leased as a private home, but is open to the public five days a year. The interior is classical in style.
Derwent Island was owned by Fountains Abbey but with the dissolution of the monasteries, it fell into the hands of the Crown and was sold off in 1569 to the Company of Mines Royal. In 1778 Joseph Pocklington bought the island (then known as Vicar's Island) and built a house, boathouse, fort and battery, and Druid circle folly on the land. Pocklington held regattas at which he fired off his cannon. Henry Marshall purchased the island in 1844 and employed architect Anthony Salvin to add a wing and a three-storey tower to Pocklington's house.