Dubhaltach Mac Fhirbhisigh (), also known as Dubhaltach Óg mac Giolla Íosa Mór mac Dubhaltach Mór Mac Fhirbhisigh, Duald Mac Firbis, Dudly Ferbisie, and Dualdus Firbissius (fl. 1643 – January 1671) was an Irish scribe, translator, historian and genealogist. He was one of the last traditionally trained Irish Gaelic scholars, and was a member of the Clan MacFhirbhisigh, a leading family of northern Connacht. His best-known work is the Leabhar na nGenealach, which was published in 2004 as The Great Book of Irish Genealogies, by Éamonn de Búrca, more than 300 years after it had been written. Family and education Mac Fhirbhisigh was most likely born at the family castle, in the parish of Lackan, Tireragh, County Sligo, sometime in the first quarter of the 17th century. He was originally known as Dubhaltach Og ("young Dubhaltach") to distinguish him from his grandfather, Dubhaltach Mór ("big Dubhaltach"). He was the eldest of four sons born to Giolla Íosa Mór Mac Fhirbhisigh and an unnamed daughter of Eoghan Gruamadha Mac Diarmada of the Sliocht Cormaic Oig Mac Diarmada of Tireragh. It is unknown whether he himself had ever married or had children. On page nine of his Introduction to The Great Book of Irish Genealogies, Nollaig Ó Muraíle writes: It is possible that he had received some sort of formal education in Galway, studying English, Latin and some Greek. This is implied by his use of all three languages in his works. There is also the possibility that he received additional training at the Mac Aodhagáin bardic school located at Ballymacegan, Lough Derg, County Tipperary, which was run by noted scholar, Flann Mac Aodhagáin. Mac Fhirbhisigh's friends and acquaintances included John Lynch, Patrick D'Arcy, Mary Bonaventure Browne, Sir James Ware, Eoin Ó Gnímh and Ruaidhrí Ó Flaithbheartaigh. His contemporaries include Peregrine O'Duignan, Mícheál Ó Cléirigh, Richard Martyn, Daibhidh Ó Duibhgheannáin, and Randal MacDonnell, 1st Marquess of Antrim. Mac Fhirbhisigh's career as a scholar overlapped with a devastating period of war, famine, and plague in Ireland (the Irish Confederate Wars of 1641–1653) but, curiously, he never mentions contemporary politics or events in his works. Emergence in 1643 The first certain date that can be associated with Dubhaltach is 5 May 1643, when he was situated at Ballymacegan translating the ancient glossary Duil Laithne ("the book of Latin"). In that year he transcribed from an old Mac Aodhagan manuscript what is now known as