Dubhaltach Mac Fhirbhisigh (Irish pronunciation: [ˈd̪ˠʊwəl̪ˠt̪ˠəx mˠək ˈɪɾʲəvʲɪʃiː]), 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.