HMP Shepton Mallet, sometimes known as Cornhill, is a former prison located in Shepton Mallet, Somerset, England. When it closed in 2013, it was the United Kingdom's oldest operating prison, and had been since the closure of HMP Lancaster Castle in 2011. Before closure Shepton Mallet was a category C lifer prison holding 189 prisoners. The prison building is grade II* listed, while the former gatehouse and perimeter walls are grade II.