Mynydd-y-glog is a hill just east of the village of Penderyn in the northern corner of the county borough of Rhondda Cynon Taff in south Wales.
Its summit plateau rises to a height of 389m / 1277 ft at OS grid ref SN 982088, a spot marked by a trig point.
To its north lies the partly dry valley of Pant Sychbant which forms the eastern extension of Cwm Cadlan.
A public footpath runs south-eastwards from the Cwm Cadlan road near Wernlas giving access from that direction.
The hill can also be gained from the west via the former railway line at Penderyn and via the Natural Resources Wales's woodlands at Penmoelallt to the east.