Coordinates: 52°59′35″N 4°25′34″W / 52.993°N 4.426°W / 52.993; -4.426
Trefor is a village on the north coast of the Llŷn Peninsula in Gwynedd, Wales. Its population, with nearby Llanaelhaearn is 1,560.
Trefor is 9 miles north from Pwllheli and 13 miles south west from Caernarfon. It is surrounded by the sea and mountains, overlooking the Caernarfon bay.
Located just off the main A499 road, Trefor has a small harbour and a beach with some sand. At the top of the beach is an emergency telephone to summon help in the event of a maritime emergency. The land behind the beach is made of boulder clay deposited during the last glaciation, and is being slowly eroded by the sea.
Rising steeply behind the village is Yr Eifl and its neighbouring hills. A granite quarry, 'Trefor granite quarry' or the Yr Eifl quarry opened there in 1850. The industrial narrow gauge railway—Trefor Quarry railway—opened in 1865 and brought rock from the quarry to the coast, but was gradually replaced by road transport and was finally closed in 1960. Trefor granite is used to make curling rocks. There is one school in Trefor, a primary school called Ysgol yr Eifl.