Maentwrog is a village and community in the Welsh county of Merionethshire, lying in the Vale of Ffestiniog just below Blaenau Ffestiniog, within the Snowdonia National Park. The River Dwyryd runs alongside the village. Its population of 585 in 2001 increased to 631 at the 2011 Census. The Community of Maentwrog includes the village of Gellilydan.