HOLYHEAD (Caer Gybi, the fort of Cybi), a seaport and town of Anglesey, North Wales, on Holy Island, at the western end of the county. Pop. (1931) 10,707. It is a terminus of the L.M. S.R. 264 m. from London by rail. The church may occupy the site of the old monastery of St. Cybi (6th or 7th century). There are traces (camps, etc.) of earlier occupation on the high ground near the town. Once a fishing village the town has since the reign of William IV. acquired importance as a packet station for Dublin. It was selected for this purpose in 18o1 and in 1815– 19 was made the terminus of the great Telford road from Eng land. The harbour protected by a breakwater (II m.) was opened in 1873. Additions were made in 1880. There is passenger traffic to Dublin and Greenore and mails are carried to Dun Laoghaire (Kingstown).