Holyhead (/ˌhəʊliˈhɛd, ˌhɒliˈhɛd/; Welsh: Caergybi pronounced [kɑːɨrˈɡəbi] , "Cybi's fort") is a historic port town, and is the largest town and a community in the county of the 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.
In the mid-19th century, Lord Stanley, a local philanthropist, funded the building of a larger causeway, known locally as "the Cobb"; it now carries the A5 and the railway line. The A55 dual carriageway runs parallel to the Cobb on a modern causeway.