This thesis is the first comprehensive study of the cult and textual profile of the Medieval Irish saint, Abbán. It presents a close analysis of the saint’s hagiographical dossier and comparatively examines his record in the medieval Irish genealogies, martyrologies and litanies. This research is conducted through five chapters, each of which is arranged in line with the chronological order of Abbán’s life. Matters concerning the saint’s ancestry are the main point of focus in Chapter 1: this chapter centres primarily on a range of genealogical entries and pedigree lists, which are then compared and contrasted with some of the hagiographical evidence for his ancestry. Chapters 2-4 deal with hagiographical evidence for Abbán’s monastic career, his cult in Ireland and overseas and also offer an examination of the textual history of his biographical account or Vita. Several key themes emerge, particularly the question of whether the extant sources reflect the merging of two geographically distinct cults of the saint; or whether two separate saints of the same name been merged into a single composite individual. These chapters also argue that the earliest extant Latin Life of St. Abbán was drawing on earlier sources which no longer survive. In Chapter 5, matters concerning Abbán’s death and two feast-days (16 March and 27 October) are brought to the fore, for which the martyrologies are the main source of evidence. Normally, a saint’s feast-day commemorates the anniversary of his/her death, meaning it is not possible for two feast-days to commemorate the same event. Chapter 5 argues that both feast-days may represent the separate interests of Abbán’s two primary foundations: Moyarney (Co. Wexford) and Killabban (Co. Laois). As Abbán’s Latin Life is untranslated, this thesis also provides a detailed English summary of each section of the Life, as an Appendix.