| Allt Lwyd | |
| Elevation M: | 653 |
| Prominence M: | 28 |
| Parent Peak: | Waun Rydd |
| Listing: | sub Hewitt, Nuttall |
| Translation: | grey slope |
| Language: | Welsh |
| Location: | Powys, Wales |
| Range: | Brecon Beacons |
| Coordinates: | 51.8611°N -3.339°W |
| Grid Ref Uk: | SO012215 |
| Topo: | OS Landranger 160 |
| Map: | Wales Powys |
Allt Lwyd is a top of Waun Rydd in the Brecon Beacons National Park, in southern Powys, Wales.
The summit is heathery and marked by a small pile of stones. It is found at the end of Waun Rydd's south-east ridge. It overlooks Talybont Reservoir, and has the Talybont Forest on its steep flanks.[1]