The Afon Nyfer (English: River Nevern) is a river in North Pembrokeshire which runs into the Irish Sea.
The river rises at Blaencwm , just east of Crymych. It flows northward then westward, skirting the slopes of the Preseli Hills. It passes through Felindre Farchog and Nevern, and reaches the sea at Newport. Its length is about 18 km.
It is significant for trout, sewin and salmon. Historically, it was an important boundary, dividing the Hundred of Cemais into Cemais Is Nyfer (to the north) and Cemais Uwch Nyfer (to the south).