Ua Bráein, Tigernach (d. 1088), abbot and scholar of Clonmacnoise, was probably one of the Uí Bráein (O'Breens) who were lords of Bregmaine (barony of Brawny, Co. Westmeath) till the seventeenth century. This family supplied several dignitaries to the monastery of Clonmacnoise, the site of which is on the east bank of the Shannon, less than 10 km downstream from Brawny. A brief death notice in the Annals of Ulster describes Tigernach as airchinnech (lay abbot) of Clonmacnoise, but a more expansive one in the Annals of the Four Masters (AFM) titles him ardchomarba (chief successor) of Ciarán (qv) and Commán (founders of Clonmacnoise and Roscommon respectively). AFM also describes him as suí leighind 7 senchusa, i.e. an expert in both ecclesiastical and traditional learning, and names the place of his death as Iomdhaidh Chiaráin, ‘Ciarán's resting-place’ – probably Tempall Ciaráin, the little church whose ruins may still be seen at Clonmacnoise.
The name of Tigernach is well known because of its attachment to one of the compilations of annals connected with Clonmacnoise, the so-called ‘Annals of Tigernach’. The main text of these survives in a fourteenth-century manuscript (Rawl. B. 488), now in the Bodleian Library, Oxford. Midway in an annal dated to 1088, a drawing of a hand indicates the statement ‘Huc usque Tigernach scribsit antequam quieuit’ (Tigernach wrote up to this point before he died), which led the Rev. Charles O'Conor (qv), who first edited the annals in 1825, to name them ‘Tigernachi Annales’, a title which apparently he adopted from Sir James Ware (qv). O'Conor was extravagant in his praise: ‘not one of the countries of northern Europe can exhibit a historian of equal antiquity, learning, and judgement with Tighernach’ – as quoted by Eugene O'Curry (qv), who endorsed this encomium: ‘Tighernach, whose name stands among the first of Irish annalists’. John O'Donovan (qv) added his tribute: ‘[Tigernach] manifests a degree of criticism uncommon in the iron age in which he flourished’, as did W. M. Hennessy (qv): ‘Tighernach, whose chronicle of Irish affairs is generally regarded as the most authentic of its kind’.
Scholars of the twentieth century were, however, more sceptical. In 1914 Eoin MacNeill (qv) established that the main text belongs to a much earlier period than the eleventh century, and expressed the belief that, at most, Tigernach may have copied some of the material, or made contemporary entries. Other scholars followed MacNeill's lead in this; Paul Walsh (qv) pointed out that what was very obviously an interpolation may have had its origins in a marginal note made by someone who knew the date of Tigernach's death, and that this was later taken into the body of the text by a copyist. Nevertheless, however tenuous the connection, successive Celtic scholars and historians continue to recall that name every time they quote from the ‘Annals of Tigernach’.