Domnall mac Eimín meic Cainnig (died 23 April 1014) was an eleventh-century Mormaer of Mar. He is attested by numerous accounts of the Battle of Clontarf in which he is said to have lost his life supporting the cause of Brian Bóruma mac Cennétig, High King of Ireland, a king whose forces fought against those of Sitriuc mac Amlaíb, King of Dublin, Máel Mórda mac Murchada, King of Leinster and Sigurðr Hlǫðvisson, Earl of Orkney. Domnall is the first Mormaer of Mar on record, and the Irish sources that note him are the earliest sources to note the province of Mar. Domnall is the only Scottish combatant recorded to have in the Battle of Clontarf. His motivations for fighting are uncertain.