The name of the Parish is taken from that of St Melaine, a 6th-century bishop of Rennes in Brittany.
Sometimes referred to as St Mellanus, the church dedicated in his honour, built in the 14th century, stands in the centre of the older part of the village, with the primary school and nearby pub, The Coryton Arms.
Also close to the village is St Mellion International Resort, offering four star accommodation and extensive golfing and leisure facilities.
The parish is located between Callington and Saltash in the east of the County (Duchy) of Cornwall and several miles to the west of the River Tamar. It is one of the smallest parishes in Cornwall with a population of less than 408 (in the 2011 census) and an area of 2,985 acres (1,207 hectares). The population is concentrated in the south-east corner of the parish with 25% of residents living in the more rural parts.
Crocadon Farm (mentioned in the Domesday Book) lies within the Tamar Valley Area of Outstanding Natural Beauty and also has a Site of Special Scientific Interest (SSSI). The parish has two further SSSIs and also lies within an Area of Great Landscape Value.