Abergavenny Castle is a castle in the town of Abergavenny, Monmouthshire. The castle has Norman origins: the motte was built by Hamelin de Ballon, the Norman conqueror of this area in 1090AD. In 1233AD the castle was destroyed by Richard Marshal, Earl of Pembroke, and the Welsh Princes. Soon after a stone keep was built on the motte and the present Victorian 'keep' probably stands on its foundations.

In 1175 Abergavenny Castle was the scene of an infamous act: the Massacre of Abergavenny. Henry, the third son of Miles Fitz walter had been killed by Seisyll ap Dynfnwal in 1175. As there were no other other male heirs, the castle and Brecknockshire and Upper Gwent passed to his mother Bertha who was a daughter of Miles Fitz walter. William de Braose decided to avenge the death of his uncle Henry. He summoned Seisyll ap Dyfnwal, his son Geoffrey, and a number of other local Welshmen from Gwent to Abergavenny Castle for a dinner--and reconciliation meeting--on Christmas Day. They were all murdered and their lands were taken.

Control of the castle passed back and forth during the turbulent years as the Welsh Marches changed hands in the twelfth century between the English and Welsh forces. During the thirteenth and fourteeth centuries a huge amount building work was undertaken on the castle whilst it was in the hands of the Hastings family. The most prominent features that remain from this period are the towers in the western corner of the castle.

The keep along with most of the other castle buildings, was damaged badly in the Civil War. In the 19th century, the present building - now the Museum - was constructed on top of the motte as a hunting lodge for the Marquess of Abergavenny.