Neide mac Onchu was an Irish lord.
Neidhe son of Onchu son of Finnlugh was described as the Cú Chulainn of the Conmaicne in an account of the battle of Ardrahan, which took place sometime about 800.
The Conmhaicne (descendants of Conmhac) were an ethnic group divided into a number of distinct branches that scattered around Ireland in the early medieval period. They take their name from a mythical ancestor known as Conmhac ("hound son"), a son of Fergus mac Róich,.
Neide's branch of the Conmaicne were located in the district once known as TrÃÂcha Máenmaige, centred on Loughrea, within which is the parish of Kilconickny (church of the Conmaicne). The Conmaicne Maonmhagh were located some distance from the other branches of the tribe, who were in north and west County Galway.
According to the account: