HM Prison Dorchester was a local men's prison, located in Dorchester in Dorset, England. The prison was operated by His Majesty's Prison Service, and closed in January 2014.

Dorchester is the county town of Dorset, England. It is situated between Poole and Bridport on the A35 trunk route. A historic market town, Dorchester is on the banks of the River Frome to the south of the Dorset Downs and north of the South Dorset Ridgeway that separates the area from Weymouth, 7 miles (11 km) to the south. The civil parish includes the experimental community of Poundbury and the suburb of Fordington.