Donn Cothaid mac Cathail, King of Connacht, died 773.^[1]

Donn Cothaid was a King of Connacht from the Ui Fiachrach Muaidhe branch of the Connachta. He was the great-grandson of Dúnchad Muirisci mac Tipraite (died 683).^[2] He was the last member of this branch to hold the throne of Connacht and ruled from 768 to 773.

Donn Cothaid's son, Connmhach mac Duinn Cothaid (died 787), was a later king of the Ui Fiachrach. A grandson, Dubda mac Conmac, was the grandfather of Aed Ua Dubhda, eponym and ancestor of the O'Dowd Chiefs of the Name.