Fan Brycheiniog is the highest peak at 2633 feet in the Black Mountain (Y Mynydd Du) region of the Brecon Beacons National Park in southern Wales. There is a trig point at the peak and on the edge of the escarpment, and nearby, a stone shelter with an inner seat. It is just inside the county of Powys, formerly Brecknockshire, the Welsh name of which gives the mountain its name. It is also within the Fforest Fawr Geopark designated in 2005 in recognition of the area's geological heritage. The views of the moorland and open country to the north are spectacular when the weather is clear, and reveals the isolation of the range, especially when compared with the more popular Pen y Fan range to the east.