Trail Running Routes in the Brecon Beacons
Four distinct areas, three very different kinds of running, and almost no flat ground anywhere in the national park.
The Brecon Beacons divide neatly for runners: the steep central Beacons around Pen y Fan, the long grassy ridges of the Black Mountains to the east, the remote Carmarthen Fans in the west, and the waterfall woodland of Fforest Fawr in between.
Pick the area by what you want out of the day, not by what is closest. The routes below are the ones we guide most often, with the figures you need to judge whether they suit you.
The routes, compared
| Route | Distance & ascent | What it's like |
|---|---|---|
| Pen y Fan Horseshoe | ~16 km / ~800 m | Steep, iconic, busy. The best short mountain day in south Wales |
| Black Mountains ridges | ~28 km / ~1,100 m | Long, grassy, fast. The endurance route of the park |
| Carmarthen Fans | ~22 km / ~900 m | Remote and exposed escarpment above two glacial lakes |
| Fforest Fawr waterfalls | 10–18 km / 300–500 m | Sheltered woodland and river trails — the bad-weather option |
Which route suits which runner
- First time on Welsh mountains — Pen y Fan Horseshoe, in settled weather.
- Training for a mountain ultra — the Black Mountains, for sustained runnable climbing.
- Wanting solitude — the Carmarthen Fans; you can run the whole escarpment and see nobody.
- Poor forecast — Fforest Fawr, where the trees give you shelter and the running is still good.
Conditions, and why they decide your route
The Beacons sit in the path of weather coming off the Bristol Channel, and the tops get a great deal more wind than the valley forecast suggests. Cloud arrives quickly on the summit plateau, the escarpment edges drop away sharply, and there is little shelter and no reliable water once you are high.
That is why we choose the route on the morning rather than weeks in advance. A guided day in the Beacons is as much about picking the right ground for the day as it is about the running.
Running these routes guided
We guide all of the routes above for individuals and small groups — route planning, navigation, pacing and safety kit handled, with the route chosen for the conditions on the day.
- A guide on every run, with route planning and navigation
- Pace grouping, so nobody is dropped and nobody is held back
- Safety kit carried by the guide, plus first-aid cover
- A personalised kit list before you travel
- Technique and pacing coaching on trail, at no extra cost
- Accommodation and transfers bundled in if you want them
Frequently asked questions
What is the best trail running route in the Brecon Beacons?
For a short, spectacular mountain day, the Pen y Fan Horseshoe. For long runnable distance, the Black Mountains ridges. For quiet and drama, the Carmarthen Fans.
Where can I run in the Brecon Beacons in bad weather?
Fforest Fawr. The waterfall and woodland trails are sheltered, the ground drains reasonably well, and you avoid the exposed tops entirely.
Do I need navigation skills to run in the Brecon Beacons?
On Pen y Fan in clear weather, no. On the Black Mountains ridges or the Carmarthen Fans in cloud, absolutely — the ground is broad and featureless.
Are there guided trail runs in the Brecon Beacons?
Yes. We run guided days across the whole park for all abilities, with the route matched to your pace and the day's conditions.
Where to go next
Want to run this with a guide?
We guide runners of every level on trails across the UK and Europe — routes planned, navigation handled, pace matched to you.