Domnall Brecc (Welsh: Dyfnwal Frych; English: Donald the Freckled) (died 642 in Strathcarron) was king of Dál Riata, in modern Scotland, from about 629 until 642.
He first appears in 622, when the Annals of Tigernach report his presence at the battle of Cend Delgthen (probably in the east midlands of Ireland) as an ally of Conall Guthbinn of Clann Cholmáin.
Domnall suffered four defeats after he broke Dál Riata's alliance with the Cenél Conaill clan of the Uí Néill.
In Ireland, Domnall and his ally Congal Cáech of the Dál nAraidi were defeated by Domnall mac Áedo of the Cenél Conaill, the High King of Ireland, at the Battle of Mag Rath (Moira, County Down) in 637.
A stanza interpolated into the ancient Welsh poem Y Gododdin refers to these events: I saw an array that came from Pentir, And bore themselves splendidly around the conflagration.