Dinas Mawddwy is a town in the community of Mawddwy in south-east Gwynedd, north Wales. It lies within the Snowdonia National Park, but just to the east of the main A470, and consequently many visitors pass the town by. Its population is roughly 600. The town marks the junction of the unclassified road to Llanuwchllyn which climbs up through the mountains to cross Bwlch y Groes at its highest point, the second highest road pass in Wales.