Medieval Irish literary sources include a number of legends relating to idols purportedly worshipped by the pagan Irish prior to the coming of Christianity. Of these the most famous is Crom Cróich of Mag Slécht, identified as the ‘king-idol of Ireland’ in the pseudohistorical lore as well as in the hagiography of Saint Patrick. This article traces the development of the various traditions relating to Crom Cróich in the medieval literary milieu and re-examines some of the evidence presented by previous scholars in support of the view that these legends could refer to an actual cult of a pre-Christian deity.