The Stowe Missal is one of the earliest surviving documents of the Early Irish church and is a key witness to the Early Irish liturgy, as well as one of the few manuscripts dating back to the Old Irish period to contain a number of continuous texts in the Irish language. This thesis investigates the origins and history of the Stowe Missal by means of a close study of the manuscript and its scribes. Chapter 1 sets out the manuscript’s contents and the makeup of its quires, and offers a detailed discussion of the Stowe Missal’s scribes. The relative order of their activities is of particular concern and it is shown that the manuscript’s Irish language texts were added to the Stowe Missal by (one of) its original scribe(s). The original purpose for which the manuscript was made is also considered. Chapter 2 examines the available evidence for the Stowe Missal’s dating and its place of origin, before considering the manuscript’s early travels. It is argued that the manuscript’s traditional dating must be reconsidered and that there are strong signs that the manuscript did not long remain where it was made. In Chapter 3, the circumstances of the Stowe Missal’s early nineteenth century rediscovery are explored by reviewing both the contemporary evidence and the more recent hypotheses for the manuscript’s history in the centuries leading up to its rediscovery. Basic editions consisting of a diplomatic transcription and normalised text of the Stowe Missal’s incomplete copy of the Gospel of John, as well as the manuscript’s Irish Tract on the Mass are presented in Appendix 1 and Appendix 2, respectively. For the latter, a new translation and full vocabulary are also included. A third appendix contains an overview of the abbreviations found in these texts.