Pen Cerrig-calch is a subsidiary summit of Waun Fach in the Black Mountains in the Brecon Beacons National Park in southern Powys, Wales.

The actual summit itself is formed from pebbly sandstone of the Marros Group (formerly the Millstone Grit Series), which also dates from the Carboniferous period.

The rounded southwestern shoulder of the hill ends abruptly at a cliff by the name of Darren (Welsh 'edge') which was formed by a sizeable landslip which most probably occurred in the early post-glacial period.

A large area of hummocky ground abounding with boulders of Old Red Sandstone lies across the slopes below Darren.

The most popular route to the summit is the approach up the southeastern spur from Crug Hywel (Table Mountain).