Cermna Finn, son of Ebric and a great, great grandson of Míl Espáine, was, according to medieval Irish legend and historical tradition, joint High King of Ireland with his brother Sobairce.
[1] The pair came to power after Cermna killed the previous incumbent, Eochaid Étgudach, in battle at Tara.
[2] Cermna ruled the southern half from Dún Cermna (which Keating identifies as Downmacpatrick in Kinsale, County Cork), Sobairce the northern half from Dún Sobairce (Dunseverick in County Antrim).
Sobairce died in the same year at the hands of Eochaid Menn, son of the king of the Fomorians.
The Lebor Gabála Érenn synchronises their reign with those of Laosthenes in Assyria and Rehoboam in Judah.