Holy Island (Welsh: Ynys Cybi, 'the island of Saint Cybi') is a small island (approx. 464 ha, 1.8 square miles) on the western side of Anglesey, Wales. It is called "Holy" because of the high concentration of standing stones, burial chambers and other religious sites on the small island. According to the 2001 Census, the population of Ynys Cybi is 13,579.
Holy Island is connected to Anglesey by causeways carrying the A5/A55 road and the main railway line to Chester and London, and the original bridge of the A5 post road.
The main settlement is the port of Holyhead, from which passenger ferries travel to Dún Laoghaire and Dublin, Ireland, and freight ferries also travel to Dublin.
Around 30 miles of the 125-mile Anglesey Coastal Path is on Holy Island.
Peripheral islands and stacks include South Stack, with its famous lighthouse. Before, and even after - the construction of lighthouses, the cliffs and jagged rocks of the island were a great danger to sailors.