Eliseus Williams, better known by his bardic name Eifion Wyn (May 2, 1867 - October 13, 1926), was a Welsh language poet, born in Porthmadog in the old county of Caernarfonshire, north Wales. The primary school in the town of Porthmadog where he lived is named after him.
His best known volumes are Telynegion Maes a Môr (1908) and Caniadau'r Allt (1927; published posthumously).