| Ogof Agen Allwedd | |
|---|---|
| Location | Llangattock escarpment, Wales, United Kingdom |
| Length | 20 miles (32.5 km) |
| Geology | Limestone |
Ogof Agen Allwedd or Agen Allwedd, is, at 20.2 miles (32.5 km), one of the longest cave systems in Wales, and the longest cave system on the Llangattock escarpment.