Domnall na Madhmann Mac Suibhne, Gallowglass, ancestor of the Mac Suibhne of north Connacht, Maghery Connacht, Clanricarde and Thomond, fl. 1419.
Mac Suibhne was a son of Eoin mac Ewan Connachtach Mac Suibhne, who was in turn a great-grandson of Murrough Mear, grandson of Murrough Mac Suibhne, who died in 1267. Domnall had brother Mulmurry and Dunsleve, from whom descendant the septs of MacSweeney Banagh and MacSweeney of Ormond.
His nickname, na Madhmann, translates as of the defeats. Marsden presumes it to refer to defeats inflicted and not suffered (p. 40). He is associated with Rath Glas in County Galway
Domnall had three known sons; Murrough Mor, Ewen and Donough. Murrough Mor's sons, Murrough Og and Rory, were the ancestors of the Mac Suibhne of north Connacht and Clanricarde, respectively. Ewen' son, Aodh, also settled in Clanricarde. Donough's sons were Aodh and Conor. Aodh settled in Maghair Connanct (the plains of Connacht) in the service of the O'Conor Don, while Conor settled in Thomond, serving the O'Brien.