Gwaunceste Hill (Welsh: Bryn Gwaun-cest) is a 542-metre-high hill in the county of Powys in east Wales. It falls within the communities of Gladestry and Glascwm around 4 km east of the village of Hundred House and about 2 km north of the hamlet of Glascwm. The headwaters of the River Arrow gather on the eastern slopes of the hill. Drainage of its western slopes is into the River Edw, a tributary of the River Wye. Two subsidiary tops to the southeast and southwest are both known as ‘Little Hill’. It is a UK listed Marilyn.