Báetán (d. 581), son of Cairell and overking of Ulaid, belonged to the Dál Fiatach dynasty. His father Cairell, allegedly a son of Muiredach Muinderg, is included in the Ulster king-lists. His mother, according to genealogical tradition, was Cummíne daughter of Furudrán. He had a brother, Demmán (d. 572), who was his immediate predecessor as overking. Although there is no mention of his wife, Báetán had at least one son, Dairchell. Certainly one of the most prominent early Ulster rulers, Báetán had great political ambition and foresight. In an attempt to counter the territorial decline of the Ulaid and the relentless encroachment of the Uí Néill, he undertook to subjugate the Dál Riata of Ireland and Scotland, under their king Áedán (qv) son of Gabrán. He also endeavoured to build up Ulster's power beyond the sea by colonising the Isle of Man. Two expeditions were sent to Man (577, 578), the colony being abandoned on his death in 581. Meanwhile, if the convention at Druim Cett was in fact held as early as 575, Báetán was the Ulster ruler outflanked by the kings of Dál Riata and of Uí Néill (Áedán son of Gabrán and Áed (qv) son of Ainmere (qv)) in collaboration with Colum Cille (qv). According to this agreement, Dál Riata was brought into the Uí Néill sphere of influence.
Báetán's career has been somewhat obscured by the synthetic historians, who count him as one of only two non-Uí Néill kings to have ‘taken Ireland’, the other being Brian Bórama (qv). Some accounts styling him ruler of Ireland and Scotland, and poems crediting him with tributes from as far away as Connacht, Munster, and the Hebrides, have been described as ‘fantasies’. Báetán's main fortress was near Knocklayd, Co. Antrim. While his reign was short, his impact was considerable even though his plans to halt and reverse the decline of the Ulaid ultimately failed. According to the Annals of Inisfallen, he was killed in battle with Colcu son of Domnall of Cenél nÉogain, fighting against the powerful Áed son of Ainmire. After Báetán's death, the overkingship of Ulster was held by two successive Cruthin dynasts, Áed Dub (qv) and Fiachnae Lurgan (qv). Báetán's nephew, Fiachnae son of Demmán, was provincial king for a year before his death in 627.