This interdisciplinary collection of essays, the proceedings of the 2017 Glenstal History Conference, examines the role of Regular Canons and Canonesses who followed the rule of St Augustine in Ireland from their emergence as an expression of the Vita Apostolica in the twelfth century through the dissolution of the monasteries in the Tudor period until their eventual disappearance in the early nineteenth century. Although the most numerous and widespread of all the religious orders in medieval Ireland, the Canonical movement has been relatively neglected in Irish monastic historiography. This volume combines the work of scholars of the history, archaeology and architecture of the movement with the research of others working on its cultural, economic, liturgical, intellectual and pastoral activities. Between them the contributors provide a fascinating insight on the Canons and Canonesses in Ireland while situating them in a broader European and ecclesial context.