This study presents a wide-ranging analysis of the making of the early seventeenth-century compilation known as the Annals of the Four Masters. It surveys the intellectual context, both Irish and European, that inspired the principal compiler, the Franciscan brother Mícheál Ó Cléirigh, assisted by laymen, Cú Choigcríche Ó Cléirigh, Cú Choigcríche Ó Duibhgeannáin, and Fearfeasa Ó Maoil Chonaire, to produce a chronological outline of Irish secular history up to 1616. By the time that Mícheál Ó Cléirigh joined the order in 1623, the Irish Franciscan college of St Anthony founded at Louvain in 1607 had become a centre of collaborative scholarly research into surviving Irish hagiographical manuscripts. Franciscan hagiographical studies were inspired by analogous contemporary European scholarship and had a key aim of promoting a positive image of Ireland's Christian heritage, thereby strengthening the case for the Catholic Church in early seventeenth-century Ireland to be recognised as the true successor of the early Church of St Patrick. The creation of a revised version of the secular history of Ireland to augment the hagiographical sources that were being separately gathered and prepared for publication was a complementary endeavour. Although he was never an ordained priest, Mícheál Ó Cléirigh's expertise, as a member of a prominent learned family of historians, in handling manuscript materials in the Irish language, made him an appropriate person to undertake such a task. The Franciscan hagiographer John Colgan was the first to use the term the ‘Four Masters’ in 1645 in appreciation of the production, indicating that it had resulted in a historical text which met the needs of the Louvain research project. While the description ‘annals’ may suggest a straightforward recitation of events and dates, the Four Masters' aim went beyond mere transcription or preservation of existing sources: the manner in which they selected, revised and restructured the material available to them offers significant indicators of their ideological concerns. The sequencing of ecclesiastical entries at the beginning of each new annalistic record and the coherent patterns of omission and addition highlight their prioritisation of certain themes in their narrative of the past. The available descriptions of those saints, whose role in the early Irish Church was identified as significant from a seventeenth-century perspective, were augmented by the Four Masters team, the same saints who were given prominence in polemical catechetical and devotional texts produced by Catholic Irish scholars on the continent, and especially the Irish Franciscans at Louvain. The revision of Patrician material in light of the recently printed ecclesiastical annals of the Counter-Reformation historian Caesar Baronius affords an instance of the influence on editorial decision of Counter-Reformation historiography. The account of the impact of the Reformation and the terminology of heresy and persecution is typical of Counter-Reformation writing of the seventeenth century for which the Franciscans served as an in important agency of transmission to Ireland. The integration of the history of religious foundations, including the Observant reform, into the overall framework of Irish history was another editorial aim. The Four Masters demonstrated a very clear understanding of the contested nature of the memory of the past and its propaganda value in the context of the social and political upheavals in early seventeenth-century Ireland and the intellectual ferment of Counter-Reformation Europe. This important study not only makes a vital contribution to source criticism and understanding of the interrelationships of extant manuscripts, and the nature of historical learning and collaborative scholarly networks that transcended confessional boundaries to include Protestant scholars, such as James Ussher, Church of Ireland archbishop of Armagh, and Sir James Ware, but equally importantly elucidates the ideological milieu in which the Annals of the Four Masters were compiled between 1626 and 1636.