Variant spellings are included, so there may be some duplication. If you know of something that should be included, please let me know
| O Braonáin Kilkenny |
| O Braonáin Galway /Dakota county, Minn |
| O Braonáin Idough & Canada (archived) |
| O Braonáin (archived) |
| O Braonáin Laois & Carlow |
| O Braonáin Ulster |
| O Braonáin Startford, Ontario and Michigan |
| O Braonáin Connacht |
| O Braonáin |
| O Cuilinn Carlow |
| O Cuilinn Co. Leitrim |
| O Donnchaidh Cavan |
| O Donnchaidh (archived) |
| O Donnchaidh |
| O Mongáin |
| O'Beirn Byrne clan |
| O'Beirn |
| O'Beirn |
| O'Beirn |
| O'Beirne Byrne clan |
| O'Beirne |
| O'Beirne |
| O'Beirne |
| O'Birne |
| O'Birne (archived) |
| O'Birne |
| O'Birne |
| O'Birne Clan O'Byrne |
| O'Birne Kilcar, Co. Donegal/Nevada |
| O'Boy |
| O'Boy (archived) |
| O'Boyle |
| O'Boyle Co. Clare |
| O'Boyle Co. Tyrone |
| O'Boyle |
| O'Boyle Belfast, South Carolina |
| O'Breen Australia |
| O'Breen (archived) |
| O'Breen |
| O'Breen |
| O'Brein Australia |
| O'Brein (archived) |
| O'Brein |
| O'Brein |
| O'Brian Australia |
| O'Brian (archived) |
| O'Brian |
| O'Brian |
| O'Brien Australia |
| O'Brien (archived) |
| O'Brien |
| O'Brien |
| O'Brine Australia |
| O'Brine (archived) |
| O'Brine |
| O'Brine |
| O'Bryan Australia |
| O'Bryan (archived) |
| O'Bryan |
| O'Bryan |
| O'Byrne |
| O'Byrne (archived) |
| O'Byrne |
| O'Byrne |
| O'Byrne Clan O'Byrne |
| O'Byrne Kilcar, Co. Donegal/Nevada |
| O'Callaghan (archived) |
| O'Callaghan (archived) |
| O'Callaghan |
| O'Carroll |
| O'Carroll |
| O'Carroll |
| O'Carroll |
| O'Carroll |
| O'Carroll |
| O'Casey Dakota county, Minn |
| O'Casey Co. Clare |
| O'Casey (archived) |
| O'Casey |
| O'Casey Tipperary/ Australia |
| O'Clery |
| O'Clery Australia (archived) |
| O'Clery U.S. |
| O'Coghlan |
| O'Conner |
| O'Conner |
| O'Conner Prince Edward Island |
| O'Conner (archived) |
| O'Conner (archived) |
| O'Conner Nova Scotia (archived) |
| O'Conner DNA project: also (O')Connor/ Connors |
| O'Conner |
| O'Conner |
| O'Conner Kilbaha, Moyvane (Newtownsandes), Co. Kerry |
| O'Connolly Connollyweb (archived) |
| O'Connolly Tuam (archived) |
| O'Connolly Co. Monaghan (archived) |
| O'Connolly Waterford & Pennsylvania (archived) |
| O'Connolly |
| O'Connolly |
| O'Connolly |
| O'Connor |
| O'Connor |
| O'Connor Prince Edward Island |
| O'Connor (archived) |
| O'Connor (archived) |
| O'Connor Nova Scotia (archived) |
| O'Connor DNA project: also (O')Connor/ Connors |
| O'Connor |
| O'Connor |
| O'Connor Kilbaha, Moyvane (Newtownsandes), Co. Kerry |
| O'Connors |
| O'Connors |
| O'Connors Prince Edward Island |
| O'Connors (archived) |
| O'Connors (archived) |
| O'Connors Nova Scotia (archived) |
| O'Connors DNA project: also (O')Connor/ Connors |
| O'Connors |
| O'Connors |
| O'Connors Kilbaha, Moyvane (Newtownsandes), Co. Kerry |
| O'Conor |
| O'Conor |
| O'Conor Prince Edward Island |
| O'Conor (archived) |
| O'Conor (archived) |
| O'Conor Nova Scotia (archived) |
| O'Conor DNA project: also (O')Connor/ Connors |
| O'Conor |
| O'Conor |
| O'Conor Kilbaha, Moyvane (Newtownsandes), Co. Kerry |
| O'Daly |
| O'Daly Armagh, Meath |
| O'Daly |
| O'Daly Australia |
| O'Dea |
| O'Dea |
| O'Dea |
| O'Delaney Prince Edward Island |
| O'Delaney 1798 Transportee |
| O'Delaney Kilkenny/Australia |
| O'Delany Prince Edward Island |
| O'Delany 1798 Transportee |
| O'Delany Kilkenny/Australia |
| O'Dempsey Laois (Queen's) & Massachussetts |
| O'Dempsey Wicklow/ Australia |
| O'Doherty |
| O'Doherty |
| O'Doherty |
| O'Doherty |
| O'Doherty Derry |
| O'Donavan |
| O'Donavan |
| O'Donel Donegal, New Zealand |
| O'Donel |
| O'Donel (archived) |
| O'Donel Via Glasgow to Philadelphia (archived) |
| O'Donel |
| O'Donell Donegal, New Zealand |
| O'Donell |
| O'Donell (archived) |
| O'Donell Via Glasgow to Philadelphia (archived) |
| O'Donell |
| O'Donnell Donegal, New Zealand |
| O'Donnell |
| O'Donnell (archived) |
| O'Donnell Via Glasgow to Philadelphia (archived) |
| O'Donnell |
| O'Donnelly Tyrone. Archived |
| O'Donnelly Fermanagh |
| O'Donoghoe Cavan |
| O'Donoghoe (archived) |
| O'Donoghoe |
| O'Donoghue Cavan |
| O'Donoghue (archived) |
| O'Donoghue |
| O'Donohoe Cavan |
| O'Donohoe (archived) |
| O'Donohoe |
| O'Donohue Cavan |
| O'Donohue (archived) |
| O'Donohue |
| O'Donovan |
| O'Donovan |
| O'Doran |
| O'Dorrian |
| O'Dowd Galbally/ Knocklong, Co. Limerick |
| O'Dowda Galbally/ Knocklong, Co. Limerick |
| O'Dowde Galbally/ Knocklong, Co. Limerick |
| O'Doyne Mayo & Lancashire |
| O'Doyne Dunn Sept Association |
| O'Doyne |
| O'Doyne |
| O'Doyne |
| O'Driscoll Cork |
| O'Driscoll (archived) |
| O'Driscoll (archived) |
| O'Duigenan |
| O'Dwyer |
| O'Dwyer Kilfeacle, Tipperary/ Australia |
| O'Dwyer |
| O'Fahey (archived) |
| O'Fahey |
| O'Fahey |
| O'Fahy (archived) |
| O'Fahy |
| O'Fahy |
| O'Farrell |
| O'Farrell (archived) |
| O'Farrell Wexford |
| O'Ferrall |
| O'Ferrall (archived) |
| O'Ferrall Wexford |
| O'Finn |
| O'Finnegan Franklin Co., NY |
| O'Flinn (archived) |
| O'Flynn (archived) |
| O'Foley Breanamore, Castlerea, Co. Roscommon |
| O'Gallagher Minnesota/Montana |
| O'Gallagher |
| O'Gara |
| O'Garra |
| O'Gorman |
| O'Gradey Clare |
| O'Grady Clare |
| O'Halloran |
| O'Hanley |
| O'Hanley Moycullen Co. Galway, Boston |
| O'Hanley Solohead area, Co. Tipperary |
| O'Hanlon |
| O'Hanlon Redmond O'Hanlon |
| O'Hara |
| O'Hara Cootehall area, Co. Roscommon |
| O'Hea West Cork |
| O'Hegarty |
| O'Higgins |
| O'Higgins |
| O'Hogan Clare |
| O'Hogan Clare/Australia |
| O'Hogan |
| O'Hurley (archived) |
| O'Hussey Dingle area, Co. Kerry; and London |
| O'Hussey |
| O'Kane (archived) |
| O'Kane New Zealand (archived) |
| O'Kane N.W. Pennsylvania (archived) |
| O'Kavanagh (archived) |
| O'Kavanagh |
| O'Keane |
| O'Keane |
| O'Keane |
| O'Keane |
| O'Kearney Co. Cavan |
| O'Kearney |
| O'Kearney Michigan |
| O'Keefe |
| O'Keefe |
| O'Keeffe |
| O'Keeffe |
| O'Kelly |
| O'Kelly |
| O'Kelly (archived) |
| O'Kelly (archived) |
| O'Kelly Kilkenny (archived) |
| O'Kelly Tipperary |
| O'Kelly |
| O'Kelly Southern U.S. states |
| O'Kelly |
| O'Kennedy |
| O'Lee Westmeath |
| O'Loghlen |
| O'Loghlen |
| O'Loghlen |
| O'Loghlen |
| O'Loghlin |
| O'Loghlin |
| O'Loghlin |
| O'Loghlin |
| O'Long Kilkenny/Nova Scotia |
| O'Longy Kilkenny/Nova Scotia |
| O'Looney |
| O'Loughlin |
| O'Loughlin |
| O'Loughlin |
| O'Loughlin |
| O'Maher Kildare |
| O'Maher Kilkenny (archived) |
| O'Maher |
| O'Mahoney |
| O'Mahoney |
| O'Mahony |
| O'Mahony |
| O'Maley Tuam (archived) |
| O'Malley Tuam (archived) |
| O'Mally Tuam (archived) |
| O'Malone Kinsale, Canada, Michigan |
| O'Malone |
| O'Malone |
| O'Malone |
| O'Meagher Kildare |
| O'Meagher Kilkenny (archived) |
| O'Meagher |
| O'Meehan Sligo (archived) |
| O'Meehan Cootehall area?, Co. Roscommon |
| O'Melaghlin |
| O'Melaghlin |
| O'Melaghlin |
| O'Melaghlin |
| O'Moloney |
| O'Moore Co. Down |
| O'Moore (archived) |
| O'Moore |
| O'Moran Mayo |
| O'Morchoe |
| O'Morchoe Sligo/Ohio |
| O'Morchoe |
| O'Morchoe (archived) |
| O'Morchoe Rathnure, Co. Wexford |
| O'Morchoe |
| O'Morchoe Knocklonogad, Garryhill, Co. Carlow |
| O'Morchoe Wexford & Prince Edward Island |
| O'Morchoe Australia |
| O'More Co. Down |
| O'More (archived) |
| O'More |
| O'Mullally (archived) |
| O'Mulligan |
| O'Mulryan Cappawhite, Co. Tipperary /Franklin Co., NY |
| O'Mulryan |
| O'Mulryan Tipperary / Long Island |
| O'Mulryan Garryhill, Co. Carlow |
| O'Mulryan |
| O'Murphy |
| O'Murphy Sligo/Ohio |
| O'Murphy |
| O'Murphy (archived) |
| O'Murphy Rathnure, Co. Wexford |
| O'Murphy |
| O'Murphy Knocklonogad, Garryhill, Co. Carlow |
| O'Murphy Wexford & Prince Edward Island |
| O'Murphy Australia |
| O'Neal Franklin Co., NY |
| O'Neal (archived) |
| O'Neal (archived) |
| O'Neal Newtownlimavady |
| O'Neale Franklin Co., NY |
| O'Neale (archived) |
| O'Neale (archived) |
| O'Neale Newtownlimavady |
| O'Neil Franklin Co., NY |
| O'Neil (archived) |
| O'Neil (archived) |
| O'Neil Newtownlimavady |
| O'Neill Franklin Co., NY |
| O'Neill (archived) |
| O'Neill (archived) |
| O'Neill Newtownlimavady |
| O'Neille Franklin Co., NY |
| O'Neille (archived) |
| O'Neille (archived) |
| O'Neille Newtownlimavady |
| O'Nolan Thurles, Co. Tipperary |
| O'Nolan Thurles, Co. Tipperary |
| O'Nolan Listowel, Co. Kerry. Archived |
| O'Nolan Ballylongford?, Co. Kerry |
| O'Nolan Garryhill area?, Co. Carlow |
| O'Rahilly |
| O'Reagan |
| O'Reardan Kerry/ USA (archived) |
| O'Reardon Kerry/ USA (archived) |
| O'Regan |
| O'Reilly (Archived) |
| O'Reily (Archived) |
| O'Rielly (Archived) |
| O'Riley (Archived) |
| O'Riordan Kerry/ USA (archived) |
| O'Roarke |
| O'Roarke |
| O'Rorke |
| O'Rorke |
| O'Rourke |
| O'Rourke |
| O'Ryan Cappawhite, Co. Tipperary /Franklin Co., NY |
| O'Ryan |
| O'Ryan Tipperary / Long Island |
| O'Ryan Garryhill, Co. Carlow |
| O'Ryan |
| O'Shea |
| O'Shea |
| O'Shee |
| O'Shee |
| O'Sullivan |
| O'Sullivan (archived) |
| O'Sullivan (archived) |
| O'Sullivan |
| O'Sullivan |
| O'Sullivan Macroom area, Co. Cork; and Glynn, Mourneabbey, Co. Cork |
| O'Sullivan |