Many works in the various fields of liturgy and history refer to a Celtic Rite that was supposedly in use in Ireland prior to the arrival of Normans in the twelfth century. The existence of this liturgical rite and its supposed suppression at the hands of the Normans are usually taken for granted in these works. However some modern liturgical scholarship has begun to question the importance (or even the very existence) of the Celtic Rite. This thesis examines the actual evidence for the Eucharist in Pre-Norman Ireland. Unlike the other Celtic regions (Scotland, Wales, Brittany, etc.) it is possible to study the Eucharist in Ireland as there still exists enough textual and historical evidence for such a study. V The main contribution of this thesis is that it provides the first major analysis of Eucharistic practice in pre-Norman Ireland in over one hundred years. Great care has been taken to situate the evidence within both the historical and liturgical contexts that are sometimes ignored in secondary literature. Both the remaining ritual texts and other texts of the period that deal with the Eucharist are studied. In addition archaeological and iconographical elements are analyzed. This provides an up to date picture of the place of the Eucharist in Pre-Norman Ireland. The results of this study seriously cast into doubt the nineteenth and early twentieth century claims of a separate Celtic Rite in Ireland. This, in turn, has its repercussions on the fields of the History of Early Christian Ireland and the study of medieval liturgy. Thus the ground is prepared for further study of medieval liturgy and the religious dimension of the Pre Norman period of Christianity and society in Ireland.