| Hirfynydd | |
|---|---|
 | |
| Highest point | |
| Elevation | 481 m (1,578 ft) |
| Prominence | 246 m (807 ft) |
| Parent peak | Fan Gyhirych |
| Listing | Marilyn |
| Coordinates | 51°45′18″N 3°40′59″W / 51.75503°N 3.68306°W |
| Naming | |
| English translation | long mountain |
| Language of name | Welsh |
| Geography | |
| Location | Neath Port Talbot, Wales |
| OS grid | SN839076 |
| Topo map | OS Landranger 170 / Explorer 165/166 |
Hirfynydd is a 481-metre-high hill in Neath Port Talbot county borough in South Wales. A Roman road, Sarn Helen, runs along its entire northeast–southwest ridge-line, a route followed by a modern-day byway. To its west is Cwm Dulais and to its southeast is the Vale of Neath. The northern end of the ridge falls away to a broad upland vale containing the Afon Pyrddin and beyond which is the Brecon Beacons National Park.
The larger part of the hill is afforested with conifers. In between the plantations are areas of past or present opencasting for coal.