Irish and Welsh have divergent literary beginnings. Irish, the first western vernacular to achieve literary status, produced hundreds of works by 1100, whereas Welsh literature is hard to quantify before then. Starting with the oldest vernacular manuscripts – Lebor na hUidre (late eleventh/early twelfth century) and the Black Book of Carmarthen (ca. 1250) – the chapter addresses the difficulties of reconstructing earlier literary activity. In Ireland, well-founded dating strategies reveal literature forming in the seventh century with legal and religious writing, and blossoming in the eighth with original narratives such as ‘The Voyage of Bran’. Church schools created a vernacular literary system closely modelled on Latin Christian learning, including a metatextual tradition which canonized Irish-language texts through commentary and glossing. This activity was promoted by professional users of the vernacular – lawyers, poets, historians – who entered into a close relationship with the church. In Wales the picture is far harder to discern. Some aspects of the Irish story – the professional orders, the church schools – are comparable, but chronology eludes us and by the time the literature becomes fully describable, in the twelfth century, it appears to be an amalgam of older traditions and Anglo-Norman influences.