Cwm Penmachno is a former quarry settlement at the head of the Penmachno valley in North Wales. The Rhiwbach slate quarry was formerly linked by the Rhiwbach Tramway to the Ffestiniog railway at Blaenau Ffestiniog. The slopes around the village provide streams which are the source of the river Machno, which flows past the larger village of Penmachno before joining the river Conwy south of Betws-y-coed.