Mynydd Nodol is a 539m high hill in Snowdonia National Park and lying within the community of Llanycil in the county of Gwynedd in North Wales. It rises above the southern shores of the reservoir Llyn Celyn about 4 km northeast of its higher neighbour Arenig Fawr. Mynydd Nodol forms the backdrop in views from the A4212 car park by the dam. The hill throws down a broad shoulder to the east.