Máel Dúin mac Conaill (died 688) was a king in 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 brother Domnall Donn, which assigns him an improbable reign of 17 years.
The general confusion of the sources makes any conclusion difficult, but while it is likely that Máel Dúin was co-ruler, with his brother Domnall Donn, of the Cenél nGabráin lands in Kintyre, it is not likely that Máel Dúin and Domnall were high kings of Dál Riata.
The next king of the Cenél nGabráin known is Eochaid mac Domangairt.