Congalach mac Conaing (died 778) was a King of Brega from the Uí Chonaing sept of Cnogba (Knowth) of the Síl nÁedo Sláine branch of the southern Ui Neill.
[1] He is listed as the successor to his uncle Dúngal mac Amalgado (died 759) in a poem in the Book of Leinster; it appears that this was just to leadership of the Uí Chonaing who were called kings of Ciannachta at this time.
They separately attacked the Uí Théig branch of the Laigin and crushed them at the Battle of Ath Cliath.
[4] Donnchad and Congalach appear as enemies in the annals and this may be due to a rivalry regarding succession to the high kingship on the abdication of Niall Frossach (died 778) of the Cenél nEógain.
[7] This war ended in the Battle of Forchalad in 778 in victory for Donnchad with Congalach and many others slain including Dúnchad mac Aléni, king of Mugdorna.