The Afon Erch is a short river on the Llŷn peninsula, Gwynedd, Wales.
It continues towarin a SSW direction towards Abererch where despite the village name, it does not enter the sea but flows west parallel to the coast for 1 mile to Pwllheli.
It is joined by the Afon Penrhos immediately west of the town, having originated around the extensive bog of Cors Geirch, a national nature reserve.
[1][2] Parts of the courses of each of these rivers occupy valleys that were formed by glacial meltwater.
Until the 16th century Aber-erch did sit at the point at which the river entered the sea but the longshore drift of the sands of Morfa Abererch diverted it west thereafter.