Holyhead is a historic port town, and is the largest town and a community in the county of Isle of Anglesey, Wales. Holyhead is on Holy Island, …Holyhead is a historic port town, and is the largest town and a community in the county of Isle of Anglesey, Wales. Holyhead is on Holy Island, bounded by the Irish Sea to the north, and is separated from Anglesey island by the narrow Cymyran Strait, having originally been connected to Anglesey via the Four Mile Bridge.