The Hexham Old Gaol (Pronounced jail) is in the town of Hexham, Northumberland, England. It is reputed to be the oldest purpose-built prison in England.
The gaol was built under the order of William Melton, the Archbishop of York, in 1330–33. It held prisoners from Hexhamshire and also, in the 16th century, from the English Middle March, before their trial in the Moothall Court Room nearby.
The gaol currently houses a museum, covering: archaeology, archives, costume and textiles, law and order, music, photography, social history, weapons and war. The collections include 15th and 16th century arms and armour, and objects of local historical interest. The Border Library holds the Butler Collection, books, recordings and music relating to the culture of the Borders.