St Mawes Castle () and its larger sister castle, Pendennis, were built as part of a defensive chain of fortresses by Henry VIII to protect the south coast of Cornwall, England, United Kingdom. This chain of coastal fortifications are known as Henrician Castles or Device Forts. St Mawes Castle was built between 1540 and 1545, halfway down the hillside on the eastern shore of the River Fal estuary to provide protection to the large inland expanse of water known as the Carrick Roads, near Falmouth.