A late-medieval Welsh poem in honour of the Anglesey saint Mechyll contains features drawn from two other cults, those of the Breton St Malo and the Manx St Maughold. This article surveys the evidence for the interpenetration of these three cults in medieval Man and Anglesey. It describes first the contents of the Welsh poem and the other evidence for the cult of Mechyll. It demonstrates that Mechyll was identified with Malo under his Latin name, Machutus, though the identification itself is unhistorical. The question of the name of Malo-Machutus, the spread of his cult and the hagiography associated with him are then surveyed. It is shown that St Maughold of Man was likewise associated with Machutus, and that much the same thing happened at the Scottish church of Lesmahagow, originally dedicated to St Féchín. The place of Maughold in the Lives of St Patrick is then discussed, confirming that Maughold of Man was the saint associated by Muirchú (c.700) with Patrick’s adversary Mac Cuill. The final question raised is the name of Maughold himself. Though it is unlikely that Maughold and Mechyll were really the same historical individual, the possibility is acknowledged.