St Cybi's Church is a medieval church near the Roman Caer Gybi in Holyhead, Anglesey, Wales. The church was Grade I listed in January 1968. The original church was constructed at Holyhead around 540 AD by St Cybi, a cousin of St David. The church was sacked by Viking invaders in the 10th century and damaged again in 1405 by Henry IV's invading force. The present church was built in the 13th century and stands near the Roman fort in Holyhead.