St Mellion (Cornish: Sen Melyan) is a village and rural civil parish in east Cornwall, England, United Kingdom.

The parish is about 3 miles (5 km) south of Callington and is in the St Germans Registration District.

[4] St Mellion is also the location of Pentillie, a 17th-century castle and estate which has been a seat of the Coryton family since 1698.

They additionally owned an estate at Newton Ferrers, also in St Mellion.

[8] Crocadon Quarry, 200 metres east of St Mellion village, is a Site of Special Scientific Interest for its geology.