Mary Tavy is a village with a population of around 600, located four miles north of Tavistock in Devon in south-west England; it is named after the River Tavy. There is an electoral ward with the same name. Its population at the 2011 census was 1,559. Mary Tavy used to be home to the world's largest copper mine Wheal Friendship, as well as a number of lead and tin mines. It lies within Dartmoor National Park. The village lies a mile or two north of Peter Tavy; both were shown as separate settlements in the Domesday Book entry of 1086.