Blathmac (d. 670), son of Máel-Cobo and overking of Ulaid, belonged to the Dál Fiatach dynasty. He was one of four brothers, among whom was Óengus, ancestor of the rulers of Leth Cathail (Lecale, east Co. Down). Blathmac had seven sons, the most distinguished of whom was Bécc Bairrche (qv), who later held the overkingship of Ulaid. Blathmac succeeded his father Máel-Cobo as king in 647. His reign was apparently peaceful till towards the end, when he engaged in a clash with the neighbouring dynasty of Dál nAraide. In this battle, which was fought at Fertas (near Belfast) in 668, Cathasach son of Luirgéne, king of Dál nAraide, was slain. When Blathmac died in 670, his immediate successor was his cousin Congal Cennfhota (qv) son of Dúnchad. Bécc Bairrche son of Blathmac did not become king till 692.
AU; AFM; Bk Leinster, i, 193; vi, 1443, 1451; O'Brien, Corpus geneal. Hib., 322, 410; Mac Niocaill, Ire. before vikings, 101; Byrne, Ir. kings, 285; NHI, ix, 132