The birlinn or West Highland galley has been used frequently as an image on clan crests, and appears on more than eighty medieval gravestones in the west of Scotland, yet not a single example of the ship itself remains or has been discovered, and definite information on its dimensions and construction is scarce. Some information about the birlinn can be gleaned from Gaelic poetry from the period 1300–1760, from oral tradition, stories, and also from land charters, estate papers, and accounts. The bìrlinn as seen on gravestone carvings appears to be closely related to the Viking ship, and my intention in this paper is to compare the West Highland vessel with the Norse vessel, using information from the square sail tradition still extant in Norway, to interpret information from the Gaelic bards. As well as increasing our practical knowledge of the bìrlinn, I hope to increase understanding of its important place in Gaelic heritage and illuminate links between Norse and Gaelic culture during the Middle Ages.