The Afon Dwyfor is a river in Gwynedd, north-west Wales. It rises in Cwm Dwyfor ( at the head of )Cwm Pennant, gathers to itself numerous streams which drain the surrounding mountains from Mynydd Graig Goch in the west to Moel Hebog in the east, then flows southwest towards Dolbenmaen and out of the Snowdonia National Park.
After a brief diversion west, it turns south, then southwest again, heading for the village of Llanystumdwy. Beyond Llanystumdwy it heads for the coast and Tremadog Bay ( Its mouth has been diverted eastwards for more than 1 km by a spit resulting from ).longshore drift.
Its principal tributaries are the Afon Henwy which enters on its left bank above Dolbenmaen, and the Afon Dwyfach which joins it as a right-bank tributary to the west of Llanystumdwy. The Dwyfach itself rises in an area of flat ground to the west of the A487 road between Bryncir and Llanllyfni and flows in a generally southerly direction.
- Owen, H.W. & Morgan, R. 2007 Dictionary of the Place-names of Wales, Gomer Press, Ceredigion, Wales
- Ordnance Survey 1:25,000 scale Explorer map sheet no 254 Lleyn Peninsula East