Holyhead Mountain (Mynydd Tŵr in Welsh: from (pen)twr, meaning tower) is the highest mountain on Holy Island, Anglesey, and the highest in the county of Anglesey, north Wales. It lies about two miles west of the town of Holyhead, and slopes steeply down to the Irish Sea on two sides. Ireland can be seen from here on a clear day and the mountain is an important site for seabirds.