Dolgellau is a town and community in Gwynedd, north-west Wales, lying on the River Wnion, a tributary of the River Mawddach. It was the traditional county town of the historic county of Merionethshire until the county of Gwynedd was created in 1974. Dolgellau is the main base for climbers of Cadair Idris and Mynydd Moel which are visible from the town. Dolgellau is the second largest settlement in southern Gwynedd after Tywyn and includes the community of Penmaenpool.

The Afon Mawddach is a river in Gwynedd, Wales, which has its source in a wide area SH820300 north of Dduallt in Snowdonia. It is 28 miles (45 km) in length, and is much branched; many of the significant tributaries are of a similar size to the main river. The catchment area is bounded to the east by the Aran Fawddwy massif and to the west and north by the Harlech dome which forms a watershed just south of Llyn Trawsfynydd.