Pen y Gaer (or Pen-y-gaer) is the location of a Bronze Age hill fort near the village of Llanbedr-y-Cennin in the Conwy valley in North Wales.
A natural defensive site, it had a long history of occupation, indicated by the complexity of the defences, which were amended over time. There are two Bronze Age cairns on the north-west slope, and nearby are extensive prehistoric and later field systems. The remains as seen today are mostly of Iron Age origin, but further earthworks, probably of medieval origin, lie on the south-eastern slopes.
The remains of the two walls of stone can be seen, as can those of a chevaux-de-frise. The entrance is to the west, and access can be gained from a car park, reached by the road from the village.