Abergavenny Castle is a ruined castle in the market town of Abergavenny, Monmouthshire, Wales, established by the Norman lord Hamelin de Ballon in about 1087. It was the site of a massacre of Welsh noblemen in 1175, and was attacked during the early 15th century Glyndŵr Rising. William Camden, the 16th century antiquary, said that the castle "has been oftner stain'd with the infamy of treachery, than any other castle in Wales.”
During the English Civil War, as the Roundheads neared the castle, Charles I ordered a slighting of the castle to prevent its useful occupation. Most of the castle buildings, including the stone keep, were destroyed.