Gretna is a rural locality in the local government areas (LGA) of Central Highlands and Derwent Valley in the Central and South-east LGA regions of Tasmania. The locality is about 20 kilometres (12 mi) south-east of the town of Hamilton. The 2016 census has a population of 211 for the state suburb of Gretna. It was formerly known as Stony Hut Plains, though the Gretna post office was known as Macquarie Plains for many years. It has a postcode of 7140.