St Mabyn () is a civil parish and village in Cornwall, England, United Kingdom. The village is situated three miles (5 km) east of Wadebridge. The parish includes a hamlet called Longstone to the east and many small manor houses, including Tregarden, Tredethy, Helligan Barton and Colquite, all built in the 16th and 17th centuries. The area of the parish is .