This thesis explores the literary figure of the mythical early Irish judge, Fíthal, from the earliest literary reference to him, c. 800, until MacPherson’s Ossian of the mid-eighteenth century. It does so by close study of the texts within which Fíthal appears, with close attention to their assumptions and purposes. From this series of close studies we can chart the developing character of Fíthal from juridical authority in the legal and legalistic texts to ideal judge or chief judge in the wider literary tradition. The thesis is divided into seven chapters, a general introduction, and one appendix. Chapter 1 contains a literature review of the major authors and disciplines which contributed to the thesis. Chapter 2 explains Fíthal’s position as a Wisdom Figure and the international background of Irish didactic literature. Chapters 3 and 4 contain the survey of Fíthal’s existence in Irish literature including discussion of the authorial intent underlying each manifestation. Chapter 5 is a new critical edition of the most important poem concerning Fíthal. Chapter 6 is a discussion of some hitherto unexplored but important facets of Fíthal’s character and an assessment of the theoretical writings which have implications for an understanding of his status. This thesis contributes to the continuing debate concerning the relationship between early Irish law and early Irish literature while simultaneously updating and revising scholarly knowledge concerning Fíthal. The thesis ranges widely over early Irish literature as it touches on Fíthal and explains his role in the literature in both its native and international context. It is hoped that this treatment of a relatively obscure but widespread figure will demonstrate how it is possible within the extant evidence to capture a character with a continuing presence in the tradition – a conclusion with considerable implications for our understanding of the tradition itself.