Cétadach was the 31st Abbot of Clonmacnoise.
Cétadach succeeded Rónán, who resigned in 823 but only died in 844.
The following events were recorded during his time as abbot: The Annals of the Four Masters state of him: Cetadach, Abbot of Cluain Mic Nois, died.
He was of the tribe of Ui Cormaic Maenmhaighe (Máenmaige).
It was in lamentation of him this quatrain was composed:All have heard it/both uncommon and common/That an abbot at Cluain like Cedadach/will never again be seen.