Llanllyfni is a village and a community in Gwynedd, Wales. It is in the historic county of Caernarfonshire. The community consists of the villages of Drws-y-coed, Nantlle, Nasareth, Nebo, Penygroes, Talysarn and the village of Llanllyfni itself. Penygroes, Llanllyfni and Talysarn are almost conjoined. As an electoral ward the 2011 census recorded a population of 1256. It is a largely Welsh-speaking village as 85% of the villagers speak Welsh as their first language. The community covers 43 square kilometres.

Gwynedd is a county in the north-west of Wales. It borders Anglesey across the Menai Strait to the north, Conwy, Denbighshire, and Powys to the east, Ceredigion over the Dyfi estuary to the south, and the Irish Sea to the west. The city of Bangor is the largest settlement, and the administrative centre is Caernarfon. The preserved county of Gwynedd, which is used for ceremonial purposes, includes the Isle of Anglesey.