Y Felinheli, formerly known in English as Port Dinorwic, is a village and community beside the Menai Strait between Bangor and Caernarfon in Gwynedd, northwest Wales.

The Menai Strait is a strait which separates the island of Anglesey from Gwynedd, on the mainland of Wales. It is situated between Caernarfon Bay in the south-west and Conwy Bay in the north-east, which are both inlets of the Irish Sea. The strait is about 25 km (16 mi) long and varies in width from 400 metres (1,300 ft) between Fort Belan and Abermenai Point to 7.5 kilometres (4.7 mi) between Puffin Island and Penmaenmawr. It contains several islands, including Church Island, on which is located St Tysilio's Church.