Calstock is a civil parish and a large village in south east Cornwall, England, United Kingdom, on the border with Devon. The village is situated on the River Tamar 6 miles (9.7 km) south west of Tavistock and 10 miles (16 km) north of Plymouth.

Cornwall is a ceremonial county in South West England. It is recognised by Cornish and Celtic political groups as one of the Celtic nations, and is the homeland of the Cornish people. The county is bordered by the Atlantic Ocean to the north and west, Devon to the east, and the English Channel to the south. The largest settlement is Falmouth, and the county town is the city of Truro.