It lies on the east bank of the Carrick Roads, a large waterway created after the Ice Age from an ancient valley which flooded as the melt waters caused the sea level to rise dramatically, creating an immense natural harbour, the third largest in the world.

St Mawes is home of St Mawes Sailing Club. There is a year-round ferry service to Falmouth.

The town takes its name from the Celtic saint Maudez (Mawe), who may have come from Ireland.

St Mawes Castle is a well-preserved coastal fortress from the time of Henry VIII, built to counter the invasion threat from the Continent.

The Agatha Christie film Murder Ahoy was filmed here.