The pursuit of 'myth' has long been an important part of Celtic studies. Are there, in fact, waifs and strays of ancient mythology preserved in medieval Celtic texts? Do myths reflect a prehistoric world-view, history, or literary innovation? And how are old myths refitted, and new myths invented, by writers in medieval and modern times? These are some of the questions compellingly addressed in the studies collected in this issue of the Yearbook, featuring groundbreaking work on: the mythological underpinnings of names in the Welsh Mabinogi; the story of Branwen and the clash between Britain and Ireland; the figure of the 'holy mermaid' in medieval Irish literature; horses, dogs, and King Arthur; and the ideological implications of 'insularity'. Contributors include Phillip Bernhardt-House, Ranke de Vries, Jessica Hemming, Catherine McKenna, and Thomas O'Loughlin.