Llandecwyn is a hamlet near Penrhyndeudraeth in Gwynedd, Wales. The bulk of the population (between 40 and 50 houses) is now located around Cilfor close to the A496 road and served by Llandecwyn railway station, with a cluster of under ten houses around the road junction at Capel Brontecwyn half a mile up the hill to the southeast, and other isolated houses and farms scattered across the hillsides. Formerly, there was a sizeable population closer to the Anglican church of Saint Tecwyn and the lakes: Llyn Tecwyn Isaf and Llyn Tecwyn Uchaf. The church now stands alone, three-quarters of a mile due east of Cilfor. There is a children's play area at Cilfor, but there are no shops or schools.