Pen Pumlumon Arwystli is the second highest summit on the Plynlimon massif, a part of the Cambrian Mountains in the county of Ceredigion, Wales.
The summit is grassy, and is marked by 3 large ancient cairns. The views include Rhos Fawr, Drygarn Fawr, Pen y Garn to the south and Aran Fawddwy, Glasgwm, Tarrenhendre and Tarren y Gesail to the north.
The longest river in Britain, the River Severn, has its source on a lower boggy plateau to the north of the summit.
- ^ Nuttall, John & Anne (1999). The Mountains of England & Wales - Volume 1: Wales (2nd edition ed.). Milnthorpe, Cumbria: Cicerone. ISBN 1-85284-304-7.