Trethevy (Cornish: Tredhewi) is a hamlet in north Cornwall, England, United Kingdom. It is midway between the villages of Tintagel and Boscastle in the civil parish of Tintagel. Trethevy has a number of historic buildings and is an early Christian site. The hamlet is divided by the B3263 road which continues through Trevalga to Boscastle: the main settlement is south-east of the road and to the north-west is the Rocky Valley.