Somhairle Mac Domhnaill (c. 1580 – c. 1632), called by English speakers Sorley McDonnell, was a renowned soldier for the Gaelic cause in Ireland and Scotland during the Thirty Years War and the patron who commissioned two 17th-century manuscript collections of poems, Duanaire Finn and The Book of O'Connor Donn.
As a result of French and English protest to the Spanish government in the Netherlands, Mac Domhnail and his men had to seek asylum in an abbey in Dunkirk.
He took part in the Bohemian campaign in the Thirty Years War and fought at the head of his company in the Verdugo regiment in the Battle of White Mountain, 1620.
He returned to the Netherlands in 1624 and spent some time in the garrison of Ostend, with the Franciscan priest Brian Mac Giolla Coinnigh as chaplain to his company He is believed to have spent his final years in penury in the Irish College of St Anthony in Leuven, where he died about 1632.
The collection of Lays in Duanaire Finn, written by the scribe and soldier Aodh Ó Dochartaigh in 1627, was published by Dr Eoin Mac Néill and Gerard Murphy in three volumes between 1908 and 1953.