Castell Henllys (Welsh, "castle of the old court") is an important archaeological site in north Pembrokeshire, Wales, between Newport and Cardigan.
This Iron Age hillfort has been the subject of an ongoing excavation for more than twenty years, accompanied by an exercise in reconstruction archaeology whereby experiments in prehistoric farming have been practised. Four roundhouses and a granary have been reconstructed on their original Iron Age foundations
During the summer the site acts as a training excavation for young archaeologists.
The site is a popular visitor attraction and is owned by the Pembrokeshire Coast National Park.