Holyhead Mountain is the highest point on Holy Island, Anglesey, and 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 cliffs below are an important site for seabirds.

Holy Island is an island on the western side of the larger Isle of Anglesey, Wales, from which it is separated by the Cymyran Strait. It is called "Holy" because of the high concentration of standing stones, burial chambers, and other religious sites on the small island. The alternative English name of the island is Holyhead Island. According to the 2011 UK Census, the population was 13,659, of whom 11,431 (84%) lived in the largest town, Holyhead.