St Mawes is a small village opposite Falmouth, on the Roseland Peninsula on the south coast of Cornwall, United Kingdom. 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. The immense natural harbour created is often claimed to be the third largest in the world. It was once a busy fishing port, but the trade declined during the 20th century and it now serves as a popular tourist location, with many properties in the village functioning as holiday accommodation. The village is in the civil parish of St Just in Roseland.