Domnall Donn (died 696) was king of Dál Riata (modern western Scotland).
His death is reported by the Annals of Ulster, but without mention of a title.
He is among the kings named by the Duan Albanach, following his father and Dúnchad mac Conaing, which assigns him an improbable reign of 13 years.
He may have been co-ruler with his brother Máel Dúin mac Conaill, or have reigned for 3 years rather than 13, making his rule 693–696 approximately.
The next king of the Cenél nGabráin known is Eochaid mac Domangairt.