Brandub (d. c.605/8), son of Eochu and overking of Leinster, belonged to the dynasty of Uí Chennselaig, which in the late sixth to early seventh century contested supremacy in Leinster with the Uí Máil dynasty. Little seems to be known about his father Eochu; he may have been a local king of Uí Chennselaig. While the genealogical tradition concerning Brandub's mother is somewhat confused, she is generally identified as the Uí Fhiachrach lady Feidelm (or Feidlimid), who is also claimed as the mother of Áedán (qv) son of Gabrán, king of Dál Riata. Tradition has it that Brandub was spared from a tribute by his half-brother on their mother's intervention. According to the ‘Banshenchas’ (love of women), Brandub was married to Cumman of the Déisi.
Brandub is first noted in the annals under the year 590, when he led the forces of Uí Chennselaig against the Uí Néill in the battle of Mag nÓchtair. He may have secured the overkingship of Leinster the following year, after the death of the Uí Máil king Áed Cerr, although the circumstances of his succession are by no means certain. He played a prominent role in the struggle between the Leinster dynasties and the emerging Uí Néill for suzerainty in the midlands, his exploits being celebrated in the Middle Irish pseudo-historical tale ‘Bóruma Laigen’. He won important victories at Dún Buchat in 597 and at Dún Bolg a year later, slaying the Cenél Conaill dynast Cummascach and his father, Áed (qv) son of Ainmere (qv), claimant to the kingship of Tara.
The ‘Bóruma’ places these battles deep in Leinster territory, in west Co. Wicklow, while the Latin Life of St Máedóc (qv) of Ferns appears to substantiate such a tradition. It may be significant that Rathbran, which some authorities associate with Brandub, is located in the same vicinity. Certainly, the ruling lineages of Uí Fhelmeda and Uí Murchada, both of which claimed descent from Brandub, were situated (in the later historical period at least) in north-east Co. Carlow adjoining Co. Wicklow. However, the annals preserve traditions of other battles involving Brandub and the Uí Néill in the north Kildare–Meath region. According to the Annals of Tigernach (Tigernach Ua Bráein (qv)), the above-mentioned encounter at Mag nÓchtair was located near Cloncurry in north Co. Kildare, while the Annals of the Four Masters (s.a. 597–600) alludes to an incursion by Brandub into Brega (east Meath). His ultimate defeat (605) at the hands of the Cenél nÉogain king of Tara, Áed Uaridnach (qv), in the battle of Slaebre, has also been placed in Meath. Again, Fir Thulach, another dynasty that claimed descent from Brandub, left its name on the barony of Fertullagh, Co. Westmeath.
The defeat of Áed son of Ainmere (598) would seem to have marked the high point of Brandub's career. He is credited with having exercised extensive power beyond the boundaries of Leinster, and it is maintained that he was a generous benefactor of the church, giving land to St Máedóc for the foundation of Ferns. Be that as it may, some time after his reversal at Slaebre, Brandub was treacherously slain in an internal conflict. There is a strong tradition that he was killed in an encounter at Damchluain (possibly Dughlone, parish of Kilmuckridge, Co. Wexford), by Sárán Saebderc, airchinnech (superior) of Senboth Sine (Templeshanbo). Brandub left several sons, the most prominent of whom was probably Ségíne, who figures in the genealogies as ancestor of the local kings of Uí Fhelmeda and Uí Murchada. The overkingship of Leinster, however, passed to Rónán son of Colmán, who apparently belonged to the Síl Cormaic lineage of Uí Chennselaig.