Eochu Fíadmuine was, according to medieval Irish legend and historical tradition, joint High King of Ireland with his brother or half-brother Conaing Bececlach.
They took power after killing the previous High King, Eochu Uairches.
According to the Lebor Gabála, Conaing remained in power in the north, while Lugaid took the south.
The Annals of the Four Masters say Lugaid ousted Conaing and took complete control of Ireland.
The Lebor Gabála synchronises the reign of Eochu and Conaing with that of Artaxerxes I of Persia (465–424 BC).