Old Irish-Gaelic Surnames
A Supplement to Ireland's History in Maps
Translation from Gaelic to English
(sorted by Anglicized Surname - disregarding O and Mac prefixes)


Gaelic Name - Anglicized name - Early County Origin - Other Roots
Mac an Bhreitheamhan - (Mac) Abraham, Abrehan, Judge - Co Cork
Ó hEachthianna - Ahern or Hearne - Co Clare - the Dal gCais (e.g. Brian Boru)
Mac an tSaoir - MacAteer - Ulster, (St. Ciaran)
Mac Amhalghaidh - MacAuley or MacAwley - Co Offaly/Westmeath, lords of Calry
Mac Amhlaoibh - MacAuley or MacAwley - Co Fermanagh - branch of MaGuire
Mac Amhlaoibh - MacAuliffe - Co Cork - branch of MacCarthy
Mac Árdghail - MacArdle - County Monaghan, Armagh and Louth of Oriell
Ó Banain - O'Banan or O'Bannion - Co Fermanagh
Ó Banain - (O) Bannon or O'Bannion - Co Tipperary
Ó Beaglaoich - Begley - Co Donegal
Ó Birn - (O) Beirne - Co Roscommon - chiefs of Tir Briuin
Ó hAimheirgin - (O) Bergin - Co Offaly - chiefs of Geashill
Ó Beolláin - (O) Boland - Co Sligo - Uí Fiachrach
Ó Beolláin - (O) Boland - Co Clare - Dalcassian
Ó Baoghill - (O) Boyle - Co Donegal
Ó Baoighealláin - (O) Boylan - Fermanagh/Monaghan - same stock as O'Flanagans
Mac Bradaigh - Brady - Co Cavan
Ó Brollacháin - (O) Brallaghan or Bradley - Co Tyrone/Derry - Cinel Feradaigh
Mac Braoin - (Mac) Breen - Ossory, Co Kilkenny
Ó Braoin - (O) Breen - Westmeath/Offaly - Lord of Brawney
Mac an Bhreitheamhnaigh - (Mac) Breheny, Judge - Co Sligo/n. Roscommon
Mac Branain - MacBrennan - Co Roscommon - chiefs of Corca Achlann
Ó Braonain - (O) Brennan - Co Kilkenny, East Galway, Westmeath and Kerry
Ó Breislein - (O) Breslin - Co Donegal, Cenel Enda, chiefs of Fanad
Ó Bric - (O) Brick - Co Waterford - of the Decies
Ó Bruic - (O) Brick - Co Kerry - originally of Thomond
Mac Giolla Bhride - MacBride or Kilbride - Co Donegal
Ó Briain - O'Brien - Munster (Thomond) - the Uí Toirdealbhaigh, part of the Dal gCais
Ó Bruadiar - (O) Broder or Broderick - Co Cork, Limerick and Galway
Ó Brógáin - (O) Brogan - Co Mayo - the Uí Fiachrach
Ó Brolaigh - (O) Brolly, Brally, Brawley - Co Donegal/Derry - Cinel Oenghusa
Ó Bróithe - (O) Brophy - Co Kilkenny, Laois
Ó Brosnacháin - (O) Brosnan - Co Kerry
Ó Buachalla - Buckley - Co Tipperary/Offaly
Ó Bogaigh - Buggy - Co Kilkenny/Wexford (origin unknown)
Mac Conboirne - Burns - N. Connaught - mainly of Scottish origin
Ó Broin - (O) Byrne, Burns - Co Kildare/Wicklow - Uí Broin sept of Crioch Branach
Mac Cába - MacCabe or McCabe - Co Cavan, etc. - a Breffny sept from the western isles of Scotland
Mac Gafraidh - (Mac) Caffrey - Co Tyrone/Fermanagh - branch of the Maguires
Ó Cathain - O'Cahan or Kane - East Donegal - Cenel Eoghain
Ó Cathail - (O) Cahill - Co Galway - chief of Kinelea
Ó Cathail - (O) Cahill - Co Kerry and also in Tipperary
Ó Ceallacháin - (O) Callaghan - Co Cork - the Eoghanacht, descent from Ceallachan
Ó Cathaláin - (O) Callan - Co Monaghan/Louth - named from a king of Fernmag.
Mac Giolla Laoire - (Mac) Callery, Colleary, Collary - Co. Sligo & north Connacht
Mac Cathmhaoil - Campbell - Co Tyrone - Cenel Fearadhaigh Theas of Cenel Eoghain
Mac Cailein - Campbell - Co Donegal - Scottish gallowglass of Cenel Eoghain
Ó Ceanndubháin - (O) Canavan - Co Galway, physicians to O'Flaherty of Connemara
Mac Cuindlis - MacCandless - Co Down
Mac Anna or Canna- MacCann - Co Armagh - lords of Clanbrassil (Cenel Eoghain)
Ó Canain - (O) Cannon - Co Galway - the Uí Maine, same stock as O'Madden
Ó Canannain - (O) Cannon - Co Donegal - Kings of Cinel Conaill (pre-1200)
Ó Caithniadh - (O) Canny - Co Mayo - Uí Fiachrach Muaidhe, chiefs of Erris
Ó an Cháintigh - (O) Canty - west Co Cork
Ó Cairbre - (O) Carbery - Co Westmeath - chiefs in Clonlonan
Ó Ciardha - (O) Carey - Co Kildare - southern Uí Neill, lords of Carbury
Ó Cearmada - (O) Carmody - east Co Clare
Mac Cearnaigh - (Mac) Carney or Kearney - Co Meath and Monaghan/Armagh
Ó Cearrnaigh - (O) Carney - Co Mayo - Uí Fiachrach
Ó Cairealláin - (O) Carolan - Co Derry - chief of Clan Diarmada
Ó Cearbhalláin - (O) Carolan - Co Cavan/Monaghan
Ó Cairre - (O) Carr and (O) Carry - various, e.g. of Cenel Aengusa
Ó Cearbhaill - (O) Carroll - Co Offaly and Tipperary - lords of Eile (Ely)
Ó Cearbhaill - (O) Carroll - Co Monaghan and Louth - chiefs of Oriel
Ó Cearbhaill - (O) Carroll - Co Leitrim/Sligo - chief of Calraighe
Ó Cearbhaill - (O) Carroll - Co Kilkenny - chief of northern Gowran
Ó Cearbhaill - (O) Carroll - Co Kerry - chief of Locha Lein
Mac Cearbhaill - (Mac) Carroll or MacCarvill - Ulster
Mac Artian - MacCartan - Co Down - chiefs of Kinelarty
Mac Carthaigh - MacCarthy - Munster (Tipperary) - the Eoghanacht
    * MacCarthy Mor - South Kerry
    * Dunhallow MacCarthys - Northwest Cork
    * MacCarthy Riabhach - Carberry, Southwest Cork
    * MacCarthy Muskerry - Cork/Kerry border
Ó Cathasaigh - (O) Casey - various, including lords of Suaithni (co. Dublin)
Mac Cathasaigh - MacCasey or Casey - Co Louth/Monaghan
Ó Caiside - Cassidy - Co Fermanagh
Mac Fhlannchaidh - (Mac) Clancy - Co Clare - Dal gCais, branch of MacNamara
Mac Fhlannchaidh - (Mac) Clancy - Co Leitrim - chief of Dartry (Rosclogher)
Ó Cleireigh(Clery) - Clark(e) - Connacht, Donegal - chiefs of Uí Fiachra Finn
Ó Cléirigh - (O) Clery or Cleary - Co Galway - Tigherneach Ua Cleirigh, lord of Aidhne
Ó Cleirchín - (O) Clerkin, Clerk, Cleary - Co Limerick - Uí Fidhgeinte, Uí-Cairbre
Ó Clochasaigh - (O) Cloghessy, Clohessy - Clare Clare, east Limerick. Dalcassian
Mac Cluin - (Mac) Clune - Co Clare
Mac Bhloscaidh - McCluskey - Co Derry - a branch of the O'Cahans
Ó Cobhthaigh - (O) Coffey - Co Cork - same stock as O'Driscolls
Ó Cobhthaigh - (O) Coffey - Co Roscommon - Uí Maine branch of the O'Maddens
Ó Cobhthaigh - (O) Coffey - Co Westmeath
Mac Cagadhain - Cogan - Co Leitrim
Ó Colmáin - Coleman - Co Sligo, barony of Tireragh - Uí Fiachrach
Ó Clúmháin - Coleman or O'Colman - Co Sligo/Cork - descendant of Clumhan
Mac Colghain - (Kil) or (Mac) Colgan - Co Offaly - same stock as O'Dempsey and O'Dunne
Ó Colghain - (O) or (Mac) Colgan - Co Derry and also of Co Donegal
Ó Coileáin - Collins - Co Limerick and later West Cork - lords of Connello
Ó Cuilleáin - Collins - West Cork - Corca Laoidhe
Ó Concheannain - (O) Concannon - Co Galway - Uí Briúin in Uí Maine, lords of Uí Diarmada
Ó Caoindealbháin - (O) Conlan, Quinlan - Co Meath, princes of Uí Laeghari
Ó Connalláin - Conlon, Conlan or Connellan - Co Galway and Roscommon
Ó Coinghiolláin - Conlon - Co Sligo
Mac Conghaile or Ó Conghaile- (Mac) Conneely - Co Galway (often confused with "Connolly")
Ó Conaill - O'Connell - Co Kerry - chief of Magunihy
Mac Dhomhnaill - Connell and MacConnell - Ulster - the Clan MacDonald
Ó Conghailaigh or Ó Conghaile - (O) Connelly or Connolly - SE Co Galway - Síl nAmnchadha Uí Máine
Ó Conghalaigh or Ó Conghaile - (O) Connolly - Co Fermanagh and Monaghan
Ó Coingheallaigh - Connolly - West Cork
Ó Congalaig - (O) Connolly - Co Dublin/Meath
Mac Canann - Mac Connon - Co Monaghan
Conchobhair - (O) Connor - Co Offaly - descent from Cathaoir Mor
    * O'Conor Don, Roe, & Sligo - Connacht, Co Roscommon
    * O'Conor Faly - Co Offaly
    * O'Conor of Corcomroe - North Clare
    * O'Connor Kerry - Co Kerry and also in Keenaught, Co Derry
Ó Maolconaire - (O) (Mul)Conry or Conroy - Co Roscommon
Ó Conraoi - (O) Conry or Conroy - Co Roscommon/Galway - Uí Maine
Mac Conraoi - (Mac) Conroy or King - Co Galway - lord of Delvin of the Two Lakes
Mac Consaidín - MacConsidine - Co Clare - Dal gCais, a branch of O'Brien
Mac Conmhaoil - MacConville or Conwell - Co Armagh (Oriel)
Ó Conbhuidhe - (O) Conway - Co Sligo
Ó Connmhacháin - (O) Conway - Co Mayo - same stock as O'Hara
Mac Connmhaigh or Connmeadha - (Mac) Conway - Thomond
Mac Conmidhe - (Mac) Conway or MacNamee - Co Derry and Tyrone
Mac Congail - Conwell or MacConwell - Co Down
Ó Cuagain - Coogan - Galway/Roscommon - the Uí Maine
Mac Giolla Chomhgaill - (Mac) Cool - Donegal
Mac Cuille or Mac Giolla Chuille - Cooley - Connacht, Roscommon, Clare, Galway.
Ó Cuana - Cooney - Co Tyrone, then north Conacht
Ó Culachain - Coolihan or O'Cuolihan - Co Mayo - the Uí Fiachrach
Mac Corcrain - (Mac) Corcoran - Co Offaly/Tipperary, chief of Clan Ruainni
Ó Corcráin - (O) Corcoran - Co Fermanagh
Mac Cormac - MacCormack - various
Ó Corraidh or Ó Corra - (O) Corr or Corry - Co Tyrone-Fermanagh
Ó Corragáin - (O) Corrigan - Co Fermanagh - same stock as Maguire
Ó Cosraigh - (O) Cosgrave - Co Wicklow, later Wexford
Ó Cosraigh - (O) Cosgrave - Co Galway - Uí Maine
Ó Cosraigh - (O) Cosgrave - Co Monaghan - chiefs of Fir Rois
Mac Oistoghín - (Mac) Costigan - Co Laois - a branch of Fitzpatrick
Mac Oitir - (Mac) Cotter - Co Cork
Mac Cochláin - (Mac) Coughlan - Co Offaly - Dal gCais, chief of Delvin MacCoughlan
Ó Cochláin - (O) Coughlan - Co Cork
Mac Coibheanaigh - Coveney - Co Kilkenny (Ossory) - in Crannagh barony
Mac Giolla Chomhgaill - MacIlhoyle or Coyle - Donegal
Ó Cadhain - Coyne, Kyne or Coen - Co Mayo - the Uí Fiachrach
Mac Ruidhri - MacCrary or MacCreary - Unknown - variant of MacRory?
Craobhach - Creagh - Co Clare - branch of the O'Neills of Clare
Ó Croidheáin - (O) Crean - Co Donegal/Sligo - Cenel Eoghain
Ó Creacháin - (O) Crehan - Co Mayo - the Uí Fiachrach
Ó Criocháin - (O) Crehan or Creighton - Co Tyrone- an Oriel sept
Mac Conchruachan - (Mac)Croghan - Co Roscommon
Mac Criomhthainn - MacCrohan - Co Kerry
Ó Croinin - Cronin - Co Cork
Ó Cruadhlaoich - Crowley - Carbery, Co Cork - Uí Briuin Ai
Ó Cuidighthigh - Cuddihy - Co Cork and Tipperary
Ó Cathaláin - (O) Culhane or Cahalane - Co Limerick - chiefs of Owney Beg
Ó Cuilinn - (O) Cullen - Co Wexford and Wicklow
Ó Cuileannáin - (O) Cullinan - Co Clare
Ó Cuileannáin - (O) Cullinan or Cullen - Co Donegal - of Mullinashee
Ó Cuileannáin - (O) Cullinane - Co Cork - Corcu Liadhe
Ó Coimín - (O) Cummins, Commons - Co Mayo
Mac Coinín - (Mac) Cunneen - Co Mayo
Ó Coinín - (O) Cunneen or Rabbit - Co Offaly and of Thomond
Ó Connagáin and Mac Cuinneagain - Cunningham - Co Sligo - Uí Fiachra
Ó Connagáin and Mac Cuinneagain - Cunningham - Galway/Roscommon - Uí Maine
Mac Toirdhealbhaigh - MacCurley, Curley or Terry - Connacht
Ó Curráin - (O) Curran - SW Connacht - Uí Maine
Ó Corraidhin - (O) Curreen or Curren - Co Leitrim
Mac Curtain - (Mac) Curtin - Co Clare
Mac Cosraigh - MacCusker - Co Tyrone - ernaghs of Clones
Ó Comhraidhe - (O) Corry and Curry - Co Clare
Ó Comhraidhe - (O) Curry - Co Westmeath - chiefs of Moygoish
Ó Dalaigh - (O) Daly - Co Westmeath - Uí Maine branch of the southern Uí Neill
Ó Dorchaidhe - (O) Darcy - Co Mayo and Galway - also of Norman origin
Ó Duibhdabhoireann - (O) Davoren - Co Clare
Ó Deághaidh - (O) Dea - Co Clare - of Inchiquin
Ó Dulchaointigh - (O) Delahunty - Co Tipperary/Kilkenny
Ó Dubhshláine - (O) Delany - Co Laois
Ó Diomasaigh or Dimmussaig - (O) Dempsey - Clanmalier between Co Laois and Offaly
Ó Duineachdha - (O) Dennehy or Denny - Co Cork
Ó Duibhdíorma - (O) Dermond, Dermott, Darby - chiefs of Breadach in Inishowen
Mac Diarmada - MacDermot - Co Roscommon/Sligo - of Mag Luirg (Moylurg)
Ó Duibheamhna - (O) Devany - Co Armagh/Down - ancient chiefs of Ui Breasail
Ó Duibhghiolla - (O) Devilly - Co Galway - the Uí Fiachrach Aidne
Ó Duibhghiolla - (O) Devilly - Co Galway - the Síol Anmchadha
Ó Daimhín - (O) Davin or Devine - Co Fermanagh - lord of Tirkennedy
Ó Doibhilin - (O) Devlin - Co Tyrone and Sligo - lords of Muinter Devlin, Cenel Eoghain
Ó Doibhilin - (O) Devlin - Co Sligo - chiefs in Corran, standard bearer to O'Connor
Ó Dubhuidhe - (O) Devoy or Deevy - Co Laois - 7 Septs of Leix, lord of Cremthainn
Ó Duilleain - Dillon - Co Westmeath, Longford and Mayo - Norman origin
Ó Daighnáin - Dinan - Co Clare and Cork
Ó Duinnín - (O) Dinneen, Dinan - Co Cork - the Corcu Laiodhe
MacDail re Deachair - (Mac) Dockery - Co Roscommon - Clan Dail re deacair (Sil Murray)
Ó Dubhchonna - Doheny or Downey - Co Cork - the Corcu Laoidhe
Ó Dochartaigh - Doherty or Dougherty - Co Donegal - Cenel Conaill, lords of Inishowen
Ó Dubhhláin or Dobhailen - Dolan - S. Roscommon and E. Galway - the Uí Maine
Ó Domhnallain - Donlan - S. Galway - the Uí Maine
Mac Donnchadha - MacDonagh - Co Cork - lords of Duhallow, branch of MacCarthy
Mac Donnchadha - MacDonagh - Co Sligo - lords of Corran, a MacDermot branch
Ó Donnagáin - (O) Donegan - Co Cork - of Muscraige Tri Maighe
Ó Donnagáin - (O) Donegan - Co Westmeath - of Críoch Dungan
Mac Duinnshléibhe - (Mac) Donlevy or Dunleavy - Co Down (Ulidia)
Mac Domhnaill - MacDonnell - Co Antrim - of Clan MacDonald
Mac Domhnaill - MacDonnell - Co Fermanagh - of Clankelly
Mac Domhnaill - MacDonnell - Clare/Limerick (Thomond)
Ó Domhnaill - O'Donnell - Co Donegal - the Northern Uí Neill
Ó Domhnaill - O'Donnell - west Clare and east Galway - the Uí Maine
Ó Domhnalláin - O'Donnellan - Co Galway - the Uí Maine, lord of Clan Breasail
Ó Donnghaile - Donnelly - Co Donegal. later Tyrone - Cinel Eoghain
Ó Donnchadha - (O) Donoghue Mór - Co Cork, Kerry - Eoghanacht Locha Lein
Ó Donnchadha - (O) Donoghue of the Glen - Co Cork. Kerry - the Eoghanacht
Ó Donnchadha - (O) Donohoe - Galway, Cavan and various
Ó Donndubháin - (O) Donovan - Co Limerick, then SW Cork - chiefs of Carberry
Ó Duacháin - (O) Doohan - Co Donegal
Ó Duighlaich - (O) Dooley - Co Westmeath, then NE Tipperary - lords of Fertullagh
Ó Deoráin or O Deoradháin - (O) Doran - Co Laois - 7 Septs of Leix
Ó Deargáin - (O) Dorgan - Co Cork
Ó Dudbhchon - (O) Doughan - Co Cork - Corcu Laoidhe sept
Ó Dubhda - (O) Dowd - Co Mayo and West Sligo - Uí Fiachrach Muaide
Ó Dunlaing - (O) Dowling - Co Laois - 7 Septs of Leix
Ó Dúnadhaigh - (O) Downey - Co Galway - lords of Sil Anmchadha
Ó Dúnadhaigh - (O) Downey - Cork/Kerry/Limerick border - of Luachair
Ó Dubhghaill - Doyle - Co Carlow, Wexford and Wicklow (Norse origin?)
Ó hEidirsceoil - (O) Driscoll - South Kerry, then West Cork - Corca Laoighde
Ó Diubháin - Duane or Devane - Co Galway - erenaghs of Killursa
Ó Dubhthaigh - (O) Duffy - Septs from Co Donegal, Roscommon and Monaghan
Ó Dubhagáin - (O) Duggan - North Cork - Fir Maighe
Ó Dubhagáin - (O) Duggan - Co Galway - in the territory of the Uí Maine
Ó Diubhgeannáin - (O) Duigenan, Deignan, Dignam, ... - Co Roscommon, Leitrim - erenaghs of Kilronan
Ó Doinn or Duinn - (O) Dunn or Dunne - Co Laois - lords of Iregan
Ó Donnchadha - (O) Dunphy - Co Kilkenny - of Iverk barony
Ó Diubháin - Dwane, Devane or Duane - Co Meath - of Knowth
Ó Diubháin - Dwane, Devane or Duane - Co Cork - Corcu Laiodhe
Ó Duibhir or O Dubhuidhir - (O) Dwyer - West Tipperary - of Kilnamanagh
Mac Aodhagáin - (Mac) Egan - Uí Maine territory, then Ormond
Mac Giolla Domhaigh - MacEldowney - Co Derry
Mac Giolla Rua - (Mac) Elroy - Co Fermanagh
Mac Conchradha - MacEnchroe or Crowe - Co Clare
Mac Inneirghe - MacEnery - Co Limerick - Uí Cairbre, same stock as O'Donovan
Ó hAonghuis - Ennis - Co Offaly and Meath - variant of O'Hennessy
Mac Fhiodhbhuidhe - MacEvoy - Co Westmeath, Laois - one of the "7 Septs of Leix"
O'Faodhagáin- Fagan - E. Airgialla (Oriel) - also of Norman origin
Ó Fathaigh - Fahy - Co Galway - Uí Máine, of Pobal Muintir Uí Fhathaigh
Ó Fallamháin - (O) Fallon - Co Roscommon - sept of the Uí Máine (Clann Udach)
Ó Fallamháin - (O) Fallon - Co Meath - of Crich na Cetach
Ó Failbhe - (O) Falvey - Co Kerry - the Corca Duibhne
Ó Fhearghaill or Fergail - (O) Farrell - Co Longford - lords of Annaly
Ó Faircheallaigh - (O) Farrelly or Farley - Co Cavan/Meath
Ó Faracháin - (O) Farren - Co Donegal - Lord of Finross
Ó Fearáin - (O) Fearon - Co Armagh (Oriel) - the Cenél Eoghain
Ó Fiannaidhe - (O) Feeney - Co Sligo/Mayo - sept of the Uí Fiachrach
Ó Fidhne - (O) Feeney - Co Galway/Roscommon
Ó Fithcheallaigh - (O) Fehilly, Field - Co Cork - sept of the Corca Laoidhe
Ó Fiachna - - (O) Feighney, Feeheny, Hunt - Co Roscommon/Sligo - of Síol Muireadhaigh
Ó Fiachra - - (O) Feighry, Feehery, Hunt - Co Tyrone
Ó Fionnaláin - (O) Fenelon - Co Westmeath - chiefs of Delvin (Delbna)
Ó Fiangusa - (O) Fennessy - Co Tipperary/Waterford - chiefs of a district near Cashel
Ó Fearadhaigh - (O) Ferry, Farry - Co Donegal - Cenél Conaill
Ó Fionnachta - (O) Finaghty, Finerty - Co Roscommon - of Síol Muireadhaigh
Ó Fionnachta - (O) Finaghty, Finerty - Co Galway/Roscommon - Uí Maine chiefs of Clanconway
Ó Fionnáin - (O) Finan - Co Mayo - Uí Fiachrach Muaighe chiefs of Coolcarney
Ó Fionn - (O) Finn - Co Sligo - chiefs of Calry
Ó Fionn - (O) Finn - Co Galway - erenaghs of Kilcolgan
Ó Fionn - (O) Finn - Co Monaghan - of Fir Rois
Ó Fionnagáin - Finnegan - Roscommon/Galway
Ó Fionnagáin - Finnegan - Cavan/Monaghan/Louth - a Breifne sept
Ó Finntighearn - Finneran - Co Westmeath? - chiefs of Uí Mella
Mac Fionbhair - Finnevar - Co Leitrim - chiefs of Muintir Greadain
Mac Giolla Mo-Cholmog - Fitz Dermot - Uí Dunchada of Dublin/Kildare
Mac Giolla Phadraig - Fitzpatrick - lords of Upper Ossory (Laois/Kilkenny)
Ó Flaithbheartach - (O) Flaherty - Co Galway - Lord of Moycullen and Iar-Chonnacht
Ó Flannagáin - Flanagan - Roscommon & Offaly
Ó Flannagáin - (O) Flanagan - Fermanagh - Cenel Cairbre of Tuath Ratha (Toora)
Ó Flannagáin - (O) Flanagan - Monaghan - Clan Ceallaigh - the MacDonnels of Clankelly
Ó Flannabhra - Flannery - Co Mayo - the Uí Fiachrach
Ó Flannabhra - Flannery - Co Limerick - the Uí Fidhgheinte, chief of Dal Cairbri
Ó Flaithre - (O) Flattery - Co Down - lords of Lecale, kings of Ulidia
Ó Floinn - (O) Flynn - Co Cork - Muscraige Uí Fhloinn
Ó Floinn - (O) Flynn - Co Cork - Corcu Laoidhe
Ó Floinn - (O) Flynn - Co Roscommon
Ó Flainn - (O) Flynn - Co Antrim
Ó Fhloinn - (O) Lynn - Co Armagh - Clanna Rury, descent from Coll Uais
Ó Fhógartaigh- Fogarty - Co Tipperary, Eliogarty - Dalcassian
Ó Foghladha - Foley - Co Waterford
Mac Giolla na Naomh - Ford - South Connacht
Mac Conshnámha - Forde or MacKinnawe - Co Leitrim - chiefs of Muintir Kenny
Ó Fuaráin - Forde or Foran - Co Cork
Macgiollarnath - Ford - southern Connemara
Ó or Mac an tSionnaigh - Fox - Co. Meath - nickname of a chief of Teffia
Ó Firghil - (O) Friel - Co Donegal - descent from Eoghan, brother of St. Columbcille
Ó Gamhna - Gaffney or Caulfield - Ossory (Laois/Kilkenny)
Mac Carrghamhna - Gaffney or MacCaron - Co Cavan and also Roscommon
Mac Conghamhma - Gaffney or Caulfield - S Galway - Uí Fiachrach Aidhne
Ó Gallchobhair - (O) Gallagher - Co Donegal - Cenel Conaill
Mac Giolla Riabhaigh - Gallery, MacAreavy, Gray - Co. Clare & elsewhere
Ó Gealbháin - (O) Galvin - Co Clare
Ó Gaibhtheacháin - (O) Gahan - Co Mayo - the Uí Fiachrach Muaide
Mag Fhionnáin - (Mac) Gannon - Co Mayo
Ó Gadhra - O'Gara - Co Sligo/Roscommon - chiefs of Luighne Connacht
Mag Fhearadhaigh - (Mac) Garry - Co Roscommon/Leitrim
Ó Gairbhith - (O) Garvey - southern Co Armagh, then Down
Ó Gairbhín - (O) Garvey or Garvin - Co Meath, then Mayo - So. Uí Neill
Ó Garbháin - (O) Garvey or Garvan - Co Cork/Kerry - same stock as O'Moriarity
Mac Gairbhín - (Mac) Garvey - Co Donegal
Mag Aodha - MacGee - Co Westmeath - of Muintir Tlámáin
Mag Aodha - MacGee - Donegal/Tyrone border
Mag Aodha - MacGee - Also of Scottish extraction, with Irish origins
Mag Aonghusa - Magennis or (Mac) Guinness - Co Down - the Dal Araidhe, lords of Iveagh
Mag Eochagáin - (Mac) Geoghegan - Co Westmeath - so. Uí Neill, chiefs of Kinalea
Mag Oireachtaigh - (Mac) Geraghty - Co Roscommon/Galway - Uí Briuin Ai (in Uí Maine)
Mac Giolla Phóil - (Mac)Gilfoyle or Powell - Co Offaly
Mac Giolla Mochuda - MacGillycuddy - Co Kerry - an O'Sullivan Mór branch
Ó Glaimhin - Glavin - Connacht - the Hy Fiachrach
Ó Glesáin - Gleeson or O'Glissane - Tipperary - same stock as O'Donegan
Mag Fhloinn - MacGlinn - Roscommon/Westmeath
Ó Gradaigh - (O) Grady - Co Clare & Limerick - the Dal gCais
Mac Congail - MacGonigle - Co Donegal
Ó or Mac Gormain - Gorman - Co Laois - Uí Bairrche
Ó Gairmleadhaigh - (O) Gormley - Raphoe, Co Donegal - of Cinel Moen (their tribe name)
Mag Shamhradháin - MacGovern / Magauran - Co Cavan - descent of Eochaidh (O'Rourke)
Mac Gabhann - MacGowan or Smith - Co Cavan
Ó Grádaigh - (O) Grady - Co Clare and Limerick
Mac Raith - MacGrath - Co Donegal/Fermanagh
Mac Raith - MacGrath - Co Clare
Ó hUaithnigh - Greene or Green - Co Cork
Ó hUaithnigh - Greene or Green - Co Clare
Mac Glaisin and Mac Giolla Ghlais - Greene or Green - Ulster
Ó Griobhtha - Griffin - Co Kerry and Clare
Mac Carrghamhna. later Ó Gramhna - (O) Growney - Co Tipperary
MagUiginn or MacGuagáin - MacGuigan - Co Tyrone - Cenel Eoghain
Mac Aonghasa or Oengussa - (Mac) Guinness or Magennis - Co Down - the Dal Araidhe
Mag Uidhir - MacGuire or Maguire - Co Fermanagh - rulers of Fermanagh
Ó hÉidin - Hade, Haide, Hayde - Co Galway
Ó hAodhagáin - (O) Hagan or Aiken - Co Tyrone - chiefs at Tullahogue
Mac Céile - MacHale - Co Mayo - also of Welsh origin
Ó haileacháin - (O) Hallahan - Co Cork/Waterford
Ó hAileagáin - (O) Halligan - Co Louth/Armagh (Oriel)
Ó hAllmhuráin - (O) Halloran - Co Clare (Thomond) - same stock as McNamaras
Ó hAllmhuráin - (O) Halloran - Co Galway - Chiefs of Clann Fearghaile
Ó hAghmaill - (O) Hamill - South Tyrone - Cenél Eoghain (Cenél Binnigh)
Ó hÁinle - (O) Hanley or Hanly - Co Roscommon
Ó hAnluain - (O) Hanlon - Co Armagh - lords of Orior
Ó hAnnáin - O'Hannon - Co Clare/Limerick - the Dal gCais
Ó hAnrachain - (O) Hanrahan - Co Clare/Limerick - the Dal gCais
Ó hAnrachtaigh - (O) Hanraghty or Hanratty - Co Armagh and north Co Louth (Uí Meith)
Ó hEaghra or Egra - O'Hara - Co Sligo - lords of Luighne with the O'Garas
Ó hÍr - O'Hare - Co Armagh - Oriel sept of Ó hÉir
Ó hEarcáin - (O) Harkin, Harkan - erenaghs of Clonska, Co Donegal
Ó hAirt - (O) Hart - Co Meath - southern Uí Neill, Four Tribes of Tara
Ó hIongardail - Harrington - Co Cork and Kerry
Ó hArrachtain - Harrington or O'Harraughton - Co Galway
Ó hArtagáin - (O) Hartigan - Co Clare/Limerick - the Dal gCais
Ó hEidedín - Hayden or (O) Headon - Co Carlow
Ó hAodha - Hayes - various counties
Ó hAodha - (O) Hea - Co Cork, Corca Laoidhe
Ó hEilidhe - Healey - Co Sligo
Ó hEaladaighthe - Healey - Muskerry, Co Cork
Ó hEilidhe - (O) Healy - Co Sligo
Ó hÉalaighthe - (O) Healy or Healihy - Co Cork
Ó hÉignigh or O hEicnig - (O) Heany or MacAnenay - Co Fermanagh - Kings of Fermanagh
Ó hEachighearna - Hearne or Ahern - Co Clare - the Dal gCais
Ó hEadroman - (O) Hederman, Hetherman, Heatherman - Co Clare/Limerick, east Cork
Ó hIfearnáin - (O) Heffernan - Co Clare/Limerick - chiefs of Owneybeg
Ó hEigceartaigh - Hegarty - Co Donegal & Derry - Cenel Eoghain
Ó hAichir - (O) Hehir or (O) Hare - Co Clare - Uí Fidhgheinte, lords of Magh Adhair
Ó hAonghusa - Hennessy or Henchy - Co Offaly - lords of Clan Cholgain
Ó hAonghusa - Hennessy - Co Dublian/Meath - chief of Gailenga Beg
Ó hAonghusa - Hennessy - Co Cork - Corca Laoidhe
Ó hInneirghe - Henry or O'Henery - Co Tyrone - chief of Cullentra
Ó hAiniarriadh - Henry - Southeast Ulster
Mac Einri - Henry - North Anthrim/Derry
Ó hOireachtaigh - (O) Heraghty - Co Galway and Mayo
Ó hEisleanáin or Ó hEislin - (O) Heslin - Co Leitrim - a sept of Breffny
Ó hIcidhe - Hickey - Co Clare & N. Tipperary - the Dal gCais
Ó hUigín - Higgins - Co Westmeath, Sligo and Mayo - Southern Uí Neill
Ó hÓgáin - Hogan - Co Clare & Tipperary - the Dal gCais
Ó hUallacháin - (O) Holohan - Co Offaly - of Clan Colgan with the O'Hennessy's
Ó hEoghanáin - (O) Honan - Co Clare and Co Cork
Ó hUaithnín - (O) Honeen, Hoyne, Greene - Co Clare and Tipperary
Ó hOdhráin - (O) Horan - Co Galway and Mayo
Ó hUallacháin - Houlihan - West Munster and Thomond
Mac Aodha or Aoidhe - MacHugh - West Galway - branch of O'Flahertys
Mac Aodha or Aoidhe - MacHugh - North Galway
Mac Aodha or Aoidhe - MacHugh - Co Fermanagh
Ó hAodha - Hughes - Ulster
Ó Urthaile - (O) Hurley - Co Clare & N. Tipperary - the Dal gCais
Ó hUirthile - (O) Hurley - West Cork
Ó hIarlatha - (O) Herlihy or (O)Hurley - Cork
Ó hEidhin - (O) Hynes or (O)Heyne -Galway - Uí Fiachrach Aidne
Mac Giolla Bháin - MacIlwaine or Kilbane - Co Sligo - the Uí Fiachrach
Mac Giolla Riabhaigh - MacIlrea, Kilrea - Co. Sligo & elsewhere
Mac Giolla Ruadh - MacIlroy, McElroy, MacGilroy, Kilroy - various
Mac Giolla Riabhaigh - MacIlwraith - Scottish
Mac an Airchinnigh - MacInerney - Co Clare - son of the erenagh
Ó Cathain - Kane or O'Cahan - East Donegal/Derry - Cenel Eoghain
Caomhanach - Kavanagh - Wexford and Carlow - descent from Donal MacMurrough
Ó Cadhla - (O) Kealy or Kelly - Co Galway - chiefs of Connemara
Ó Caollaidhe - (O) Kealy or Kelly - of Uí Buide, Co Laois
Ó Caollaidhe - (O) Kealy - of Uí Bercháin, Co Kilkenny
Ó Cathain - Keane - Co Galway (or Thomond) - Uí Fiachra Aidne
Ó Cein - Kean - Co Waterford
Ó Cearrnaigh - Kearney - Co Clare - Dalcassian
Mac Cearnaigh - Kearney - Ulster - Cenel Eoghain
Ó Catharnaigh - Kearney - Co Meath & Offaly - chiefs of Teffia
Ó Ciardha - (O) Keary - Co Kildare - the Southern Uí Neill, lords of Carbury
Ó Géibheannaigh - (O) Keaveney - Co Galway - the Uí Maine
Ó Caoimh or Caim - O'Keefe - Co Cork - descent from Art, King of Munster (742-762)
Ó Cianáin - (O) Keenan - Co Monaghan/Louth (Oriel)
Ó Caomháin - (O) Keevan or Kavanagh - Co Sligo - Uí Fiachrach
Ó Céileachair - Kelleher - Co Clare - the Dal gCais
Ó Ceallaigh - (O) Kelly - E Galway & S. Roscommon - Uí Maine (or Hy Many)
Ó Ceallaigh - (O) Kelly - Co Meath - O'Kellys of Breagh
Ó Ceallaigh - (O) Kelly - Co Laois - 7 Septs of Leix
Ó Caellaighe - (O) Kelly - Ossory, Kilkenny/Laois border
Ó Ceallaigh - (O) Kelly - Co Antrim and Down - Cinel Eachrach
Mac Cionath - MacKenna - Co Meath and Monaghan - southern Uí Neill
Ó Cinnéide - Kennedy - Co Clare/Tipperary - the Dal gCais - lords of Ormond
Ó Cionnaoith - (O) Kenny - Co Galway/Roscommon - Uí Maine
Ó Caoinnigh - (O) Kenny or Keeney - Co Leitrim/Donegal - lords of Muinter Kenny
Ó Coinne or O Coinnigh- Kenny or MacKenna - Co Down
Mac Eochaidh - Keogh - S. Roscommon - the Uí Mhaine, lords of Magh Finn
Mac Eochaidh - (Mac) Keogh - West Tipperary
Mac Eochaidh - Keogh - N. Kildare - same stock as the O'Byrnes
Mac Eoghain - MacKeon - Co Sligo/Leitrim
Ó Ciabháin - (O) Kevane or Kavanagh - Co Cork - Corcu Laoidhe
Ó Cadhla - Kiely - Co Clare/Limerick - the Dal gCais
Ó Céirín - (O) Kieran or Kearns - Co Mayo - chiefs of Costello
Ó Ciarain - Kerin or Carey - Co Cork/Clare
Mac Giolla Rua - Kilroy, Gilroy - Co. Clare & elsewhere
Ó Cinnfhaelidh - (O) Kinnealy - Co Limerick
Chennselaig or Cinnsealach - Kinsella - Co Wexford - see MacMurrough
Ó Ciardubháin - (O) Kirwan - Co Galway - one of the Tribes of Galway
Ó Leathlaobhair - (O) Lalor or Lawlor - Co Leix - 7 Septs of Leix
Ó Longáin - (O) Langan or Long - Co Armagh chiefs
Ó Lonagáin - (O) Lanigan - Co Tipperary chiefs
Ó Lorcáin - (O) Larkin - Co Wexford - chief of Fothart
Ó Lorcáin - (O) Larkin - Co Armagh - chief of Farney and West Uí Breasail
Ó Lorcáin - (O) Larkin - Co Galway - the Uí Maine
Ó Lorcáin - (O) Larkin - Co Tipperary - eranaghs of Lorrha
Mac Lochlainn - MacLaughlin - Co Donegal (Inishowen) - the Northern Uí Neill
Ó fLaithbheartaigh - (O) Laverty or Laherty - Co Donegal - lords of Aileach
Ó Limhain - (O) Lavin - Co Roscommon
Ó Laochdha - Leahy - Co Cork - Corca Laoighde
Ó Laoghaire - (O) Leary - Co Cork
Ó Léanacháin - Lenaghan, Linehan or Lenihan - Co Roscommon, Limerick/Tipperary
Ó Leannain - Lennon - Galway, Mayo and Fermanagh
Mac Giolla Mhín - MacLiveen - South Down
Ó Longargain - (O)Lonergan - Co Tipperary
Ó Longain - Long or (O)Langan - Co Armagh
Ó Longaigh - Long - Co Cork
Ó Lochlainn - (O)Loughlin or Lochlain - Co Clare - lord of Corcomroe
Ó Maoilsheachlainn - MacLoughlin or O Melaghlin - Co Meath - of Malachy II (southern Uí Neill)
Mac Lochlainn - MacLoughlin - Co Donegal - northern Uí Neill
Ó Labhradha - (O)Lowry or Lavery - Co Down and Ulster
Ó Lúinigh - (O)Lunney - Co Donegal/Tyrone - Cenel Moen
Ó Loideáin - Lydon, Leyden or (O)Liddane - Co Galway/Mayo
Ó Loinsigh - (O) Lynch - various including chiefs of the Dal Riada
Ó Loinsigh - Lynch - Co Galway - Norman origin, one of the Tribes of Galway
Ó Laighin - Lyons or Lyne - Co Galway and Kerry - Firbolg origin
Ó Liatháin - Lyons or Lehane - Co Cork and Limerick - Uí Fidhgheinte (also a Norman name)
Mac Maolruanaidh - Macarooney - Co Fermanagh
Ó Macdha - (O) Mackey - Co Tipperary - an Ormond sept
Ó Madaidhin or Matudain- Madden - East Galway - Uí Maine tribe
Mac or Mag Aodha - Magee - West and East Ulster (respectively)
Mag Uidhir - Maguire - Co Fermanagh - rulers of Fermanagh
Ó Meachair- Maher or Meagher - North Tipperary
Mac Mathghamha - MacMahon - Co Monaghan - rulers of Oriel (Airgialla)
Mac Mathghamha - MacMahon - Co Clare - the Dal gCais, descent from Mahon O'Brien
Ó Mathghamhna - (O) Mahony - Co Cork - Cenel Aodha, of the Eoghanacht
Ó Máille - O'Malley - Co Mayo - chiefs of Fir Umaille, or Hymalia
Ó Maoil Eoin - Malone - offshoot of the O'Connors of Connacht (?)
Ó Maoileoin - Malone - Co Clare and Wexford - assoc. with the Abbey of Clonmacnois
Ó Mainnín - Mannion or Manning - Co Galway - Pictish origin
Mac Maghnais - MacManus - Co Roscommon - from Maghnais, son of Turlough O'Connor
Mac Maghnais - MacManus - Co Fermanagh - from Maghnuis Maguire, son of Donn Mor
Ó Meadhra - O'Mara or O'Meara - Co Tipperary - chief of Uí Fahy
Mac Giolla Mhartain - Martin or Gilmartin - Co Tyrone - Uí Neill
Ó Miadhachain - Meehan or Meighan - offshoot of MacCarthys of Desmond
Ó Midhir - (O) Meere - Co Clare - Anglo origin
Ó Mealláin - (O) Mellan - Co Tyrone - Cenél Eóghain of Meallanacht
Ó Maoilédigh - (O) Melody - Co Clare/Galway - Corcomroe
MacMeanman -MacMenamin - Co Donegal/Tyrone - Cenél Conaill
Ó Muilleoir - Miller - Co Antrim - Scottish origin, Clan McFarlane
Ó Mochain - Mohan or Moen - Kilmacduagh, Galway and Killaraght, Sligo
Ó Maolmhuaidh - Molloy or Mulloy - Co Offaly - Southern Uí Neill
Ó Maolmhuaidh - (O) Molloy - Offaly - Southern Uí Neill, lords of Fercal
Ó Maoil Aodha - Molloy or Miley - Co Roscommon / East Galway
Ó Maol Dhómhnaigh - Moloney, Mullowney or Maloney - Co Clare - Chiefs of Kiltannon (Dal gCais)
Ó Manachain - Monaghan - East Roscommon - rulers of the 3 Tuathas
Ó Manachain - Monaghan - Co Fermanagh - the Fir Manach based in Lurg
Ó Maonaigh - Mooney - Co Offaly and various other
Ó Móráin - Moran - Co Mayo, near Ballina
Ó Mughráin - Moran - Galway/Roscommon - the Uí Maine, chief of Criffon
Ó Mórdha - (O) More or Moore - Co Laois - leading sept of the 7 Septs of Leix
Ó Murchain - Morgan - Co Managhan - mainly a name of Welsh origin
Ó Muircheartaigh - (O) Moriarty - South Kerry - same stock as O'Donoghues
Ó Muirgheasa - Morris - Co Sligo - the Uí Fiachrach
Ó Maolchathaigh - (O) Mulcahy - Co Tipperyary
Ó Maoldúin - (O) Muldoon - Co Fermanagh - chiefs of Lurg
Ó Maoldúin - (O) Muldoon - Co Clare (Thomond) - the Uí Bloid
Ó Maoldúin - (O) Muldoon - Co Sligo - Uí Fiachrach
Ó‘Maoldoraidh - O'Muldory - Donegal - Tirconnel (MacAlinions)
Ó Maoldomhnaigh - Muldowney - Co Kilkenny
Ó Maolchathail - (O) Mulhall or Mulcahill - Co Laois - descendant of the devotee of (St.) Cathal
Ó Maolchalann - Mulholland - N. Limerick - descendant of the devotee of (St.) Calann
Maoilchiaráin - Mulkerrin, Mulkieran - Roscommon, Galway, Ulster - devotee of (St.) Ciaran
Ó Maolalaidhs - O'Mullally or Lally - Co Roscommon - the Uí Maine
Ó Maolain - Mullan, Mullin(s), Mullen, Mullane - Co Galway - descent from Maolan
Ó Maolain - Mullan, Mullin(s), Mullen, Mullane - Co Derry - followers of the O'Cahans
Ó Maoilédigh - (O) Mulledy - Co Westmeath/Offaly - Ballymaledy
Ó Maolain - Mullins and Mollins - Cork and Monaghan (respectively)
Ó Maolagáin - (O) Mulligan - Co Donegal - chiefs of Tir MacCarthain
Ó Maolchaoine - (O) Mulqueen - Co Clare, Limerick - Dalcassian, from St. Caoine
Ó Maolruanaidh - Mulrooney - Co Fermanagh and in Mayo/Roscommon
Ó Maoilriaghain or Mael Riain- O'Mulryan or Ryan - Co Limerick/Tipperary
Ó Murnain - Murnane - Murnane - Co Limerick
Mac Murchada - MacMurrough - Co Wexford (Hy Chennselaig) - descendant of Murchadh
Ó Murchadha and Mac Murchadha - Murphy - Co Tyrone - the Cenel Eoghain
Ó Murchadha - Murphy - Co Wexford (Hy Felimy)- descendant of Murchadh or Murrough
Ó Muireachaidh - Murray - Roscommon/Galway - the Uí Maine
Ó Muireadhaigh - Murray - West Ireland - including a sept of the Uí Maine
Mac Muireachaidh - (Mac)Murry or MacMorrow - Co Leitrim
Ó Muircheartaigh - Murtagh or MacMurtry - Co Meath
Mac an Fhailghigh - Nally or MacNally - Co Roscommon and Mayo - Norman origin
Mac Con Uladh - MacNally or MacAnally - Co Armagh and Monaghan (S.E. Ulaid)
Mac Conmara - MacNamara - Co Clare - the Dal gCais, rulers of Clancullen
Mac Conmidhe - MacNamee or Conway - Co Derry and Tyrone
Ó Neachtain - (O) Naghten - Co Clare - Dalcassian
Ó Neachtain - (O) Naughton or Naghten - Co Roscommon/Galway - the Uí Maine
Ó Neill- O'Neill - Co Tyrone/Derry/Donegal - the Cenel Eoghain, rulers of Tir Eoghain
Mac an Fhilidh - (Mac) Neilly, Neely - Co Antrim
Mac Aonghasa - MacNiece - Co Antrim
Ó Niallain - Neilan or Neylan - Co Clare (Thomond)
Mac an Airchinnigh - Nerney - Co Roscommon - son of the erenagh
Ó Nuallain - Nolan - Co Carlow - princes of Foharta (Fothairt)
Ó hIonmhaineáin - (O) Noonan - Co Cork
Mac Phaidin - Patterson - Ulster (and Scotland)
Ó Peatáin - Peyton or Patton - Co Donegal - Cenél Moen
Ó Faolain- Phelan or Whelan - Co Waterford - rulers of the Decies
Ó Coigligh - Quigley - Co Mayo - the Uí Fiachrach
Ó Cuill - (O) Quill - Co Cork and Kerry
Mac an Choilgh - MacQuilly or Cox - Co Roscommon
Ó Caoindealbháin - (O) Quinlan or Kindellan - Co Meath - southern Uí Neill
Ó Cuinn - (O) Quinn - Co Tyrone - Cenel Eoghain
Ó Cuinn - (O) Quinn - Co Clare (Thomond) - the Dal gCais
Ó Cuinn - (O) Quinn - Co Antrim - the Glens of Antrim
Ó Cuinn - (O) Quinn - Co Longford - same stock as O'Ferralls of Annaly
Ó Cuirc - (O) Quirke - Co Tipperary - chiefs of Muscraighe Cuirc
Ó Raithbheartiagh - (O) Rafferty - Co Donegal/Sligo
Mac Raghnaill - MacRannall or Reynolds - Co Leitrim - lords of Muintir Eolais
Ó Reachtagáin - (O) Ratigan - Co Roscommon - coarbs of St. Finnen
Ó Riordan - Rearden or (O)Riordan - Co Tipperary/Cork - followers of the Lords of Muskerry
Ó Rodáin - (O) Reddan - Co Clare - stewards to O'Brien and MacNamara
Ó Riagáin - (O) Regan - Co Meath/Dublin - the Four Tribes of Tara
Ó Raogáin - (O) Regan or Reagan - Co Limerick - the Dal gCais
Ó Riada - (O) Reidy - Munster - king of Aradh in the 12th century
Ó Raghallaigh - (O) Reilly - Co Cavan - Uí Briuin Breifne
Ó Maolcraoibhe - Rice - Co Louth/Armagh - also of Welsh origin
Ó Ruanaidh or O Mael Ruanaid - Rooney - Co Down
Ó Roghan - (O) Rogan - Co Down - of Armagh and Iveagh
Mac Ruaidhri - MacRory or MacCrory - Co Tyrone
Ó Ruairc - (O) Rourke - Co Leitrim/Cavan - the Uí Briuin - rulers of Breifne
Ó Ruaidhín - (O) Ruane or Rowen - Co Mayo - the Uí Fiachrach
Ó Ruadháin - (O) Ruane or Rowen - Co Galway - the Uí Maine
Ó Riaghain - Ryan - Co Carlow - chiefs of Uí Drona, also see Mulryan
Ó Scannláin - (O) Scanlan - Munster
Mac Scannláin - (Mac) Scanlan - Louth (Oriel)
Ó Scolaidhe - (O) Scully - Co Westmeath
Ó Scolláin - Scullion or (O) Scully - Co Derry
Ó Seasnáin - Sexton - Thomond (also an English name)
Ó Seanachain- (O) Shanahan - Co Clare - Uí Bloid (Dal gCais)
Mac Seanlaoich - (Mac) Shanly - Co Leitrim - MacShanly of Dromod
Ó Seanáin - (O) Shannon - Carlow/Wexford
Mac Giolla t-Seanáin - (O) Shannon - Co Clare - son of the follower of St. Senan
Mac Searraigh - MacSharry or Foley - Breifne, e.g. northern Leitrim, Sligo
Ó Seachnasaigh - (O) Shaughnessy - Kiltartan, Co Galway - the Uí Fiachra Aidhne
Ó Seaghdha or Segda - (O) Shea - South and East Kerry - Lords of Iveragh
Ó Siodhacháin - Sheehan - Co Limerick/Cork - the Dal gCais
Ó Sirideáin - Sheridan - Co Longford/Cavan
Ó Seiridh or Mac Seiridh - O'Sherry or McSherry - Oriel, e.g. Monaghan and Armagh
Mac an Ghirr - Short, Shortman or Shortel - Unknown
Ó Sluaghain or O’Sluagahadain - Sloan - of Scottish origin
Mac Gabhann - Smith or MacGowan - Co Cavan
Ó Sóchlacháin - (O) Solan, Solahan - Co Mayo
Ó Spealáin - (O)Spillane - Co Tipperary, then Cork & Kerry
Ó Spealáin - Spillane or Spelman - Co Sligo
Ó Suileabháin - (O) Sullivan - Co Kerry - the Eoghanacht - O'Sullivan Mor of Kenmare Bay
Ó Suileabháin - (O) Sullivan - Co Cork - Eoghanacht - O'Sullivan Beare of Beara Peninsula
Mac Suibhne - Sweeney or MacSweeny - Co Donegal - descent of Scottish chief in Argyle
Ó Tarpaigh - (O) Tarpy, Tarpey, Torpey - Co Sligo - lords of Carra
Mac Tighearnáin - (Mac) Tiernan or Kiernan - Co Cavan - chiefs of Teallach Donnchadha
Mac Tighearnáin - (Mac) Tiernan - Co Roscommon - descent of O'Connor
Ó Tighearnaigh - (O) Tierney - Co Mayo - lords of Carra
Ó Tighearnaigh - (O) Tierney - Co Galway, Limerick and Tipperary - Ormond's Fir O'Tyernie
Ó Tuathail - O'Toole - Co Kildare and Wicklow - descent from Tuathal, king of Laigin
Ó Treasaigh - (O) Tracy or Treacy - Co Cork, Galway, Leix (Lords of Slievemargy)
Ó or Mac Tréinfhir - Traynor - Co Meath
Ó Tiobraide - (O) Tubridy - Co Clare
Ó Tuama - O'Twomey or Toomey - Co Cork, and Co Limerick
Mac an Bháird - (Mac) Ward - Co Donegal and Galway
Ó Faolain - Whelan or Phelan - Co Waterford - rulers of the Decies

Note: This list is not meant to be comprehensive. There are many variant spellings and origins of Irish names. If you have a name you would like to see added, send the information along.
This list excludes some of the notable Irish names with Norman and Welsh origins such as Burke, Butler, FitzGerald, Power, Walsh, etc. These surnames all have their rightful place in Irish History, but do not have the Gaelic name origins needed for this list. A link to the Norman and Cambro-Norman surnames is listed below.

This compilation is a result of many hours of personal research, and as such is a copyright of Dennis Walsh (2003), All Rights Reserved. If you would like to use portions of this page for non-commercial purposes please let me know - contact information.


Click this link to search for Irish Surname Histories
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Further Reference:
Norman and Cambro-Norman Surnames of Ireland
Old Irish Kingdoms and Clans
Early Tribes and Septs - by Province
Ireland's History in Maps - home page



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