Fan Brycheiniog is the highest peak at a height of 802.5 metres (2,633 ft) (above sea level) in the Black Mountain (Y Mynydd Du) region of the Brecon Beacons National Park in southern Wales.

The path leads on to Picws Du and Waun Lefrith above the smaller glacial lake of Llyn y Fan Fach.

Its summit and southern slopes are formed from the hard-wearing sandstones of the overlying Plateau Beds Formation which are of upper/late Devonian age.

There is a Bronze Age burial cairn at the summit of Fan Foel, and it was excavated in 2002–4 with the results published in 2014 in Archaeologia Cambrensis.

The round barrow was about 16 metres (about 52 feet) wide and was badly eroded with stones from the structure removed to build a central cairn by passing walkers.

There is great similarity to the early Bronze Age barrows on the summits of Pen y Fan and Corn Du, which are also exposed to show the internal cists and outer kerbstones.

The climate was warmer than currently, judging by the evidence of extensive settlement and cultivation of the high land during the British Bronze Age.

The Red Kite survived decades of persecution in this area, and has now repopulated much of England and Wales, thanks to campaigns run by the RSPB for example.