port and resort on Holy Island (Ynys Gybi), Isle of Anglesey (Anglesey, Isle of) county, historic county of Anglesey (Sir Fon), Wales. Holyhead and Holy Island, just off the west coast of Anglesey island, bear many traces of prehistoric, Celtic, and Roman occupation. In 1801 Holyhead was selected as a port for trade with Ireland, but the chief stimuli to its growth came with a new main road from the English town of Shrewsbury (1815–19) and, later, the railway from Chester. Holyhead's harbour was improved with a breakwater in 1873 and was enlarged by 1880. It has regular ferry service to Dún Laoghaire (Dún Laoghaire–Rathdown), Ireland, near Dublin. Other attractions on Holy Island include Holyhead Mountain and South Stack Lighthouse. Pop. (2001) 11,237.