Irish genealogy is the study of individuals and/or families who originated on the island of Ireland.
Genealogy was cultivated since at least the start of the early Irish historic era. Upon inauguration, Bards and poets are believed to have recited the ancestry of an inaugurated king to emphasise his hereditary right to rule. With the transition to written culture, oral history was preserved in the monastic settlements. Dáibhí Ó Cróinín believed that Gaelic genealogies came to be written down with or soon after the practise of annalistic records, annals been kept by monks to determine the yearly chronology of feast days (see Irish annals).
Its cultivation reached a height during the Late Medieval Era with works such as Leabhar Ua Maine, Senchus fer n-Alban, Book of Ballymote, De Shíl Chonairi Móir, Book of Leinster, Leabhar Cloinne Maoil Ruanaidh and the Ó Cléirigh Book of Genealogies. This tradition of scholarship reached its zenith with Leabhar na nGenealach, composed mainly between 1649–1650 in Galway.
Genealogy had at first served a purely serious purpose in determining the legal rights of related individuals to land and goods. Under Fenechas, ownership of land was determined by Agnatic succession, female ownership being severely limited.
Over time, genealogy was pursued for its own merits by the Gaelic learned classes. From c. 1100, various families such as Ó Cléirigh, Mac Fhirbhisigh, Ó Duibhgeannáin, Mac Aodhagáin and Mac an Bhaird became professional historians. They were often employed by ruling families, the most important of whom included Ó Conchobhair, Ó Neill, Ó Domhnaill, Ó Cellaigh, Mac Murchadha Caomhánach, Mac Carthaigh, Ó Briain, Ó Mael Sechlainn, Mac Giolla Padraig. It also became pervasive among the Anglo-Irish, with the recording of the family trees of FitzGerald, Butler, Burke, Plunkett, Nugent, Bermingham and others.
Some clans, such as Mac Fhirbhisigh and Ó Duibhgeannáin were originally hereditary ecclesiastical families, while others (Ó Cléirigh, Mac an Bhaird, Ó Domhnallain) were dispossessed royalty who were forced to find another profession (see also Irish medical families).
The transmission of this body of lore (seanchas) has resulted in detailed knowledge on the origins and history of many of the tribes and families of Ireland. An anglicised tradition has continued since the 17th-century, translating many of the scripts into English. The practise of genealogy continues to be of importance among the Irish and its diaspora. Historians (such as Dáibhí Ó Cróinín and Nollaig Ó Muraíle) consider the Irish genealogical tradition to have the largest national corpus in Europe.
The Irish Genealogical Doctrine
Over the course of several centuries, an evolving genealogical dogma created by the bardic viewed all Irish as descendants of Míl Espáine. This ignored variant traditions, including those recorded in their own works. The reasons behind the doctrine's adoption is rooted in the policies of dynastic and political propaganda.
The doctrine dates from the 10th–12th centuries, as demonstrated in the works of Eochaid ua Flainn (936–1004); Flann Mainistrech (died 25 November 1056); Tanaide (died c. 1075); and Gilla Cómáin mac Gilla Samthainde (fl. 1072). Many of their compositions were incorporated into the compendium Lebor Gabála Érenn.
It was enhanced and embedded in the tradition by successive generations of historians such as Seán Mór Ó Dubhagáin (d.1372), Gilla Íosa MacFhirbhisigh (fl. 1390–1418) and Flann Mac Aodhagáin (alive 1640). By 1600 it was refined to the point that certain Anglo-Irish families were given spurious Gaelic ancestors and origin legends, such was their immersion in Gaelic culture.
The first Irish historian who questioned the reliability of such accounts was Dubhaltach Mac Fhirbhisigh (murdered 1671), whose massive Leabhar na nGenealach included disparate and variant recensions. Unlike Geoffrey Keating Foras Feasa ar Éirinn, he did not attempt to synthesise the material into a unified whole, instead recording and transmitting it unaltered. However, historians as late as such as Eugene O'Curry (1794–1862) and John O'Donovan (1806–1861) sometimes accepted the doctrine and a nationalistic interpretation of Irish history uncritically. During the 20th century the doctrine was reinterpreted by the work of historians such as Eoin MacNeill, T. F. O'Rahilly, Francis John Byrne, Kathleen Hughes (historian), and Kenneth Nicholls.
The following are manuscripts consisting of genealogies in whole or part.
- Leabhar Adhamh Ó Cianáin
- Book of Ballymote
- The Book of the Burkes
- Leabhar Cloinne Maoil Ruanaidh
- Crichaireacht cinedach nduchasa Muintiri Murchada
- Cuimre na nGenealach
- Leabhar na nGenealach
- Great Book of Lecan
- An Leabhar Muimhneach
- Ó Cléirigh Book of Genealogies
- Leabhar Ua Maine
- Rawlinson B 502
- Senchus fer n-Alban
- Leabhar Clainne Suibhne
- Book of Leinster
- Book of Lecan
- MS H.2.7
- MS Laud 610
- Psalter of Cashel
- Book of Cuanu
- Book of Dub Dá Leithe
- Leabhar Airis Cloinne Fir Bhisigh
- Leabhar Airisen Ghiolla Iosa Mhec Fhirbhisigh
- Synchronisms of Flann Mainstreach
- The Chronicle of Ireland
- Norse and Norse-Gaelic pedigrees from the Great Book of Lecan (section) 
Irish Genealogical Office
Burke's Peerage and Landed Gentry
21st-century Irish genealogy
Notable Irish families
Notable Irish genealogists
- Eochaid ua Flannacáin, 936–1004
- Flann Mainistrech, died 1056
- Gilla Cómáin mac Gilla Samthainde, fl. 1072
- Gilla Críst Ua Máel Eóin, died 1127
- Néidhe Ó Maolconaire, died 1136
- Amhlaoibh Mór mac Fir Bhisigh, died 1138
- Gilla na Naemh Ua Duinn, died 1160
- Amhlaoibh mac Fir Bhisigh, fl. c. 1200
- Domhnall na Sgoile Mac Fir Bhisigh, fl.c. 1250
- Giolla Íosa Mac Fir Bisigh, died 1301
- Tanaide Mor mac Dúinnín Ó Maolconaire, died 1310
- Domnall Ó Cuindlis, died 1342
- Lúcás Ó Dalláin, fl. 14th-century.
- Seán Mór Ó Dubhagáin, died 1372
- Adhamh Ó Cianáin, died 1373
- Ádhamh Cúisín, fl. c. 1400
- Murchadh Ó Cuindlis, fl. 1398 – 1411.
- Giolla Íosa Mór Mac Fhirbhisigh, died 1418
- Giolla na Naomh Ó hUidhrín, died 1420
- Giolla na Naomh Mac Aodhagáin, died c. 1443
- Geoffrey Keating, 1569–1644
- Flann Mac Aodhagáin, alive 1640
- Cú Choigcríche Ó Cléirigh, fl. 1624–1664
- Dubhaltach Mac Fhirbhisigh, compiler of Leabhar na nGenealach, died 1671
- James Terry, Jacobite Officer of Arms, died 1725
- Charles O'Conor (historian), 1710–1791
- John Burke, creator of Burke's Peerage, 1787–1848
- William Betham, Ulster King of Arms, died 1853
- John O'Donovan (scholar), 1806–1861
- John O'Hart, popular genealogical writer, 1824–1902
- Edward MacLysaght, Chief Herald, died 1984
- Nollaig Ó Muraíle, academic historian, born 1948
- Council of Irish Genealogical Organisations
- National Archives of Ireland
- Irish Manuscripts Commission
- National Library of Ireland
- Genealogical Society of Ireland
- Public Record Office of Northern Ireland
- Irish Genealogical Research Society
- Chief of the Name
- The Standing Council of Irish Chiefs and Chieftains
- Clans of Ireland
- Dublin City Public Libraries and Archive
- Griffith's valuation
- Census of Ireland, 1911
- The Complete Peerage
- MS 1467, allegedly written in 15th-century Ireland.
- Annála Ríoghachta Éireann: Annals of the kingdom of Ireland by the Four Masters, from the earliest period to the year 1616, compiled 1628–1635, Mícheál Ó Cléirigh et al (edited and translated by John O'Donovan, 1856)
- Leabhar na nGenealach, Dubhaltach MacFhirbhisigh, compiled mainly 1649–1660, published 2004–2005
- Blake Family Records, Martin J. Blake, volume one, 1902 and volume two, 1905
- Leabhar Chlainne Suibhne: An Account of the Mac Sweeney Families of Ireland, with Pedigrees, Paul Walsh (priest), 1920
- The Learned Family of O Duigenan, Paul Walsh, Irish Eccleastical Record, 1921
- Topographical Poems by Seán Mór Ó Dubhagáin and Giolla na Naomh Ó hUuidrain, James Carney (scholar) (ed.), 1943
- Poems on the Butlers of Ormond, Cahir and Dunboyne, AD 1400–1650, James Carney (scholar), editor, 1945
- A Genealogical History of the O’Reillys, from Irish of Eoghan Ó Raghallaigh, James Carney (scholar), editor, 1950
- Poems on the O’Reillys, James Carney (scholar), editor, 1970
- The Surnames of Ireland, Edward MacLysaght, 1978
- A British Myth of Origins?, John Carey (Celticist) in History of Religions 31, pp 24–38, 1991
- Early Irish and Welsh Kinship, Thomas Charles-Edwards, Oxford, 1993
- Seán Ó Donnabháin, An Cúigiú Máistir, Nollaig Ó Muraíle, in Scoláirí Gaeilge: Léchtaí Cholm Cille XXVII, Eag. R. Ó hUiginn. Maigh Nuad, 1997, Lch. 11–82
- Irish genealogical collections: the Scottish dimension, Nollaig Ó Muraíle, in International Congress of Celtic Studies 10 (1995), pp. 251–264, 1999
- Iris Mhuintir Uì Dhonnabháin, O'Donovan History 2000, Published by the O'Donovan Clan, Skibbereen, Ireland. Article by Michael R. O'Donovan
- The Tribes of Galway, Adrian James Martyn, Galway, 2001
- Royal Roots, Republican Inheritance – The Survival of the Office of Arms, Susan Hood, Dublin, 2002
- "They’re family!": cultural geographies of relatedness in popular genealogy, Catherine Nash, in Sara Armed, Anne-Marie Fortier and Mimi Sheller eds. Uprootings/Regroundings: Questions of Home and Migration, Berg, Oxford and New York, 179–203, 2003
- Leabhar na nGenealach, Dubhaltach Mac Fhirbhisigh, 2003–2004
- Genetic kinship, Cultural Studies, 18(1): 1–34, Catherine Nash, 2004.
- Irish Origins, Celtic Origins: Population Genetics, Catherine Nash, Cultural Politics, Irish Studies Review, 14 (1): 11–37, 2006
- Of Irish descent: origin stories, genealogy, & the politics of belonging, Catherine Nash, Syracuse University Press, 2008. ISBN 978-0-8156-3159-0
- The Importance of Genealogy in Gaelic Society
- Irish surnames and Y-DNA at AncestralJourneys.org
- O'Connor, Roderic, A Historical and Genealogical Memoir of the O'Connors, Kings of Connaught, and their Descendants. Dublin: McGlashan & Gill. 1861.
- O'Donovan, John and the Rt. Hon. Charles Owen O'Conor Don, The O'Conors of Connaught: An Historical Memoir. Dublin: Hodges, Figgis, and Co. 1891.
- T. F. O'Rahilly Papers
- Chief Herald of Ireland.
- An Irish Arms Crisis — Critical essay on status of the Office of the Chief Herald.
- Full text and explanatory memorandum of Genealogy & Heraldry Bill, 2006.
- De Praesulibus Hiberniae Commentarius, Sir James Ware, 1665
- Ogygia: seu Rerum Hibernicarum Chronologia & etc. ..., Ruaidhrí Ó Flaithbheartaigh, 1685 (published and translated into English by Rev. James Hely, 1783)
- A dissertation on the origin and antiquities of the antient Scots, and notes, critical and explanatory, on Mr. O'Flaherty's text, Charles O'Conor (historian), included in The Ogygia vindicated: against the objections of Sir George Mackenzie, king's advocate for Scotland in the reign of king James II, by Ruaidhrí Ó Flaithbheartaigh, 1775
- On the Heathen State and Topography of Ancient Ireland, Charles O'Conor, 1783
- Lecturers on the Manuscript Materials of Ancient Irish History, Eugene O'Curry, 1861, a collection of 21 lectures
- Ireland before the Normans, Donnchadh Ó Corráin, Dublin, 1972
- A New History of Ireland: Volume IX: Maps, Genealogies, Lists: A Companion to Irish History, Part II: Maps, Genealogies, Lists Vol 9, ed. Theodore William Moody, F. X. Martin, and Francis John Byrne, 1984
- The Irish genealogies as an onomastic source, Nollaig Ó Muraíle, in Nomina No.16, pp. 23–47, 1992
- The Irish Genealogies: Irish History's Poor Relation?, Nollaig Ó Muraíle, London: Irish Texts Society, 2016. ISBN 9780957566187
- Placenames and early settlement in county Donegal, Dónall Mac Giolla Easpaig, in Donegal: History and Society, edited by William Nolan, Liam Ronayne and Mairéad Dunlevy. Dublin, 1996. pp. 149–182.
- Irish Kings and High-Kings. 3rd revised edition, Dublin: Four Courts Press, 2001. ISBN 978-1-85182-196-9
- A New History of Ireland, volume one, Dáibhí Ó Cróinín, Dublin, 2006