Castell Henllys (Welsh, "castle of the old court") is an archaeological site near Nevern in north Pembrokeshire, Wales.

Castell Henllys Iron Age Fort

Location within Wales
Coordinates	52°01′01″N 4°44′42″W / 52.017°N 4.745°W / 52.017; -4.745
Type	Archaeological open-air museum
Website	Castell Henllys

The Iron Age hillfort has been the subject of an ongoing excavation since the start of the 21st century, 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 – some 2,000 years old – the hillfort the only site in Britain where this has been done.^[1] The Castell Henllys site includes significant earthworks and fortifications.^[2]

During the summer the site provides training for young archaeologists and is a popular visitor attraction.^[3] It is owned by Pembrokeshire Coast National Park.