Leabhar Breathnach Annso Sis: The Irish Version of the Historia Britonum of Nennius. It is generally agreed that Lebor Bretnach dates to the mid or late 11th century. Traditionally there had been an assumption that the translation had been an Irish work, but Clancy has argued for a Scottish provenance, suggesting an origin at Abernethy, though probably intended for an Irish readership that had perhaps become interested in Scottish literature and history as a result of the military success and prestige of the Kingdom of Alba.

This ascription is now in doubt, and the historian Thomas Owen Clancy has suggested that Lebor Bretnach was instead only intended to be dedicated to Gilla Cóemáin. In two manuscripts of Lebor Bretnach, H and M, the translation is ascribed to the poet Gilla Cóemáin (fl. It only summarises the Historia Brittonum where that work deals with specifically Gaelic matters already familiar to scholars in Ireland and Scotland, and in some other passages it includes additional material taken from, for example, the Sex Aetates Mundi, Bede's Historia Ecclesiastica Gentis Anglorum, and a Pictish king-list. Lebor Bretnach is a translation of a 9th-century historical collection purportedly written by Nennius, the Historia Brittonum, but not an entirely literal one. Dublin, Royal Irish Academy, MS 23 P 2 (535) and Dublin, Trinity College, MS H. Known as the Book of Uí Maine, written before 1423. Dublin, Royal Irish Academy, MS Stowe D ii 1. Probably written in the 14th or early 15th century. A 14th-century manuscript known as the Book of Ballymote. Dublin, Royal Irish Academy, MS 23 P 12 (536). A 12th-century fragment in the Lebor na hUidre.ī.

Dublin, Royal Irish Academy, MS 23 E 25 (1229). Lebor Bretnach exists in five manuscripts: It may have originated in Scotland, although it has traditionally been attributed to the Irish poet Gilla Cóemáin. Lebor Bretnach, formerly spelled Leabhar Breathnach and sometimes known as the Irish Nennius, is an 11th-century historical work in Gaelic, largely consisting of a translation of the Historia Brittonum.

Historia brittonum