Fan Brycheiniog is a mountain in the Brecon Beacons National Park in South Wales.

It is the highest peak in the western Black Mountain region of the park. The Beacons Way, a waymarked long distance footpath forks near the mountain, with one option passing over the summit and along the long ridge , and the other option offering a lowland route passing beside the lake Llyn y Fan Fawr to the east of the summit. This path leads to the mountain from Llanddeusant in the north-west and Glyntawe in the south-east.

In winter the mountain is spectacular , & and in summer provides great views &