The County Gaol, situated in North Parade, Monmouth, Wales, was Monmouthshire's main prison when it was opened in 1790. It served as the county jail of Monmouthshire and criminals or those who fell foul of the authorities were hanged here until the 1850s and some 3,000 people viewed the last hanging. The jail covered an area of about an acre, with a chapel, infirmary, living quarters and a treadmill. It was closed in 1869. In 1884 most of the building was demolished, and today nothing remains but the gatehouse which is a Grade II listed building. Within the gatehouse, there exists "a representation in coloured glass of the complete original buildings". It is one of 24 buildings on the Monmouth Heritage Trail.