Saltwood Castle is a castle in Saltwood village, one mile (2 km) north of Hythe, Kent, England. Of 11th century origin, the castle was expanded in the 13th and 14th centuries. After the Norman Conquest, the castle was appropriated by the Archbishop of Canterbury Lanfranc and remained the property of the archbishops, with some interruptions, until 1540, when Thomas Cranmer was compelled to cede it to Henry VIII. The castle is reputed to have been the meeting place of the four knights who carried out the assassination of Thomas Becket in 1170. By the 19th century, it was "largely ruinous" and restorations to make portions of the castle habitable were carried out in the 1880s and 1930s. In the late 19th century, the castle was bought by an ancestor of Bill Deedes, the journalist and politician, who grew up there. In the 20th century, it was sold to Sir Martin Conway who commissioned Philip Tilden to undertake a restoration. In 1953, the castle was bought by the art historian Kenneth Clark (1903–1983), and then became the home of his son, the politician and diarist, Alan Clark (1928–1999). It remains the private home of his widow, Jane Clark. The castle is a Grade I listed building.

Saltwood is a village and civil parish in the Folkestone and Hythe District of Kent, England. Within the parish are the small hamlets of Pedlinge and Sandling.