Cadbury Castle is the name given to the site of an ancient Iron Age hill fort in the parish of South Cadbury in the county of Somerset, England, and is one of several sites in the British Isles that has been purported to be the location of King Arthur's legendary capital of Camelot. Today all that remains of the fort is a large mound rising up in the middle of the countryside.

Circumstantial evidence as a possible location for Camelot is compelling in that the site was actively used as a fortress in the historical period that Arthur is presumed to have lived (5th century AD), is close to the River Cam, and is near two villages named West Camel and Queen Camel. If Arthur was indeed conceived at Tintagel as tradition asserts, and was a Dumnonian Prince, Cadbury Castle would have been on the eastern frontier of his lands, and would have made sense strategically as a home base from which to do battle with the Saxons invading from the east.

The name "Cadbury" is common, and may simply mean "battle fort," but some scholars have suggested that it means "Cador's fort," after Arthur's alleged associate King Cador of Cornwall.