Domhnall mac Raghnaill was a Hebridean noble in the late 12th and early 13th centuries. He is the eponymous progenitor of Clan Donald (Clann Dhòmhnaill, "Children of Donald"). For this reason some traditions accumulated around him in the later Middle Ages and early modern period. His vast impact on culture and in the centuries remains today. Despite his role as the historical figurehead of one of the world's most famous kindreds and surnames, there is almost no contemporary evidence yielding certain information about his life.

His place in the genealogical tradition of the MacDonalds is the only reason for believing in his existence, a genealogical tradition that not all historians have accepted. Beyond his actual existence, there is little that is certain. Three entries in Irish annals may discuss him, though he is never named; a praise poem surviving from the early modern period may be descended from a poem originally written for him; a miracle in a Manx chronicle may or may not have Domhnall as its subject; and a doubtful charter surviving from a similarly late era was allegedly issued by him.

Domhnall was, reputedly, the son of Raghnall (fl. 1192), son of Somhairle (died 1164). The 17th-century History of the Macdonalds by Hugh MacDonald of Sleat claimed that Domhnall's father Raghnall had married a daughter or sister of the early-14th-century hero Thomas Randolph, Earl of Moray. Sellar suggested that this tradition may have derived from a garbled version of reality. Perhaps, Sellar argued, his mother was a daughter of William fitz Duncan. The latter was another famous earl of Moray, but one who lived in the 12th rather than the 14th century.

In a charter to Paisley Abbey Domhnall's father Raghnall is given a wife named Fonia (Fionnghuala?), though there is no direct proof that this was the name of Domhnall's mother. Raghnall, carrying the legacy of his own father Somhairle, was a powerful Argyll and Hebridean magnate who, depending on context, bore the titles 'King of the Isles', 'Lord of Argyll and Kintyre', and 'lord of the Hebrides' (Inchegal). His father's legacy was such that he became the ancestor figure of both Clann Ruaidhrí and Clan Donald.

There are no certain contemporary notices of Domhnall, and Domhnall's existence is not explicitly attested in any reliable contemporary source datable to any particular year. However, in 1212, Domhnall may have been one of the "sons of Raghnall" who suffered some kind of military defeat at the hands of the men of the Isle of Skye. The Annals of Ulster, reporting for the year 1209, recorded that:

A battle was fought by the sons of Raghnall, son of Somhairle, against the men of Skye, wherein slaughter was inflicted upon them.

A similar report from the same source has the "sons of Raghnaill" join in a raid on the Irish city of Derry led by Tomás Mac Uchtraigh, brother of Alan, Lord of Galloway. Under the year 1212 it related that:

Tomás Mac Uchtraigh, with the sons of Raghnall, son of Somhairle, came to Derry of St. Colum-Cille with six and seventy ships and the town was greatly destroyed by them and Inis-Eogain was completely destroyed by them and by the Cenél Conaill.