During the medieval period, Bardsey Island (Ynys Enlli) became a prominent and unique pilgrimage destination in North Wales. Compared to the other major shrines in the country, Bardsey stands out in several respects. The island and the many traditions connected to it continue to have deeply-felt cultural resonance among the Welsh people. This thesis examines why Bardsey developed into a pilgrimage destination in the Middle Ages and played a significant role in Welsh ecclesiastical history. Located off the Llu0177n Peninsula and across one of the most dangerous sea crossings in Britain, Bardsey provides an ideal case study to examine a unique pilgrimage destination and the peninsular route-ways leading to it. The results of this project contribute broadly to the fields of medieval archaeology and pilgrimage studies by utilizing an interdisciplinary approach of archaeological evidence, anthropological theories, Celtic hagiography, and phenomenology.