Elfin was a ruler of Alt Clut, a Brittonic kingdom based on Dumbarton Rock, sometime in the later 7th century. According to the Harleian genealogies, he was the son of Eugein I, one of his predecessors as king, and the father of Beli II, who ruled some time later.[1] Very little is certainly known of him, though he may be identifiable with other figures attested in the Irish annals, and circumstantial evidence may link him to a number of important events during this time.