An application of Georges Dumézil's tripartite diagnostic for Indo-European to the primary sources of Irish mythology (medieval manuscripts but also folklore collected in the 20th century). Comparison is made not only with the structures and remains of other traditions but also with structures in the wider field of Indo-European linguistics. Where this study differs from others in the same field is the "pincer attack" used - the author is a native speaker of Irish and so checked out all the texts in the original but is also a linguist with considerable experience of other Indo-European languages, including Vedic Sanskrit. If the reader finds that, despite its undoubted shortcomings, this analysis helps to situate the myths of the Irish gods in their wider, Indoeuropean, context, then it will have served its purpose.