| Hen Gaer | |
| Map Type: | Wales Ceredigion |
| Map Size: | 200px |
| Location: | Near Bow Street, Ceredigion, Wales |
| Coordinates: | 52.4403°N -4.0127°W |
| Gbgridref: | SN 633 844 |
Hen Gaer is an Iron Age hillfort, on a hill adjacent to and east of Bow Street, Ceredigion, Wales.
Other names of the hillfort are Broncastellan and Caer Shon.
Hen Gaer ("Old Castle") is smaller than a typical tribal fortification. It is strongly defended; the single rampart is about wide and 3m–4mm (10feet–13feetm) above the interior, with a rock-cut external ditch. On the north-east side, carefully laid stone blocks of the original rampart wall can be seen. The main entrance is on the west side. There is a circular mound outside the entrance: it is not an earlier barrow, but may be a defensive feature.[1]
The enclosed area includes some of the southern hillslope; it is thought this may have been to make the fortification visible from the narrow valley below, at the confluence of Afon Stewi and Nant Seilo forming Afon Clarach.