Celtic Names with the Prefix O
Name. | County. |
O’Ahern, | Cork. |
O’Baire, | Cork. |
O’Bannan, | King’s, Mayo. |
O’Begley, | Cork, Donegal. |
O’Behan, | King’s. |
O’Beirne, | Roscommon. |
O’Billry, | Limerick. |
O’Birn, | Mayo. |
O’Bligh, | Mayo. |
O’Bolger, | Carlow, Kilkenny. |
O’Boylan, | Monaghan. |
O’Boyle, | Donegal. |
O’Bradley, | Cork, Donegal. |
O’Branagan, | Louth. |
O’Bree, | Kilkenny. |
O’Brennan, | Kerry, Kilkenny. |
O’Breslin, | Donegal, Fermanagh, Tipperary. |
O’Bric, | Waterford. |
O’Brien, | Clare, Cork, Limerick, Tipperary, Waterford. |
O’Brien or Mac-I-Brien. | Tipperary. |
O’Brigan, | Cork. |
O’Brodar, | Donegal, Kilkenny. |
O’Brody, | Mayo. |
O’Brogan, | Cavan, Mayo, Queen’s, Sligo. |
O’Brolchan, | Londonderry. |
O’Brosnaghan, | Kerry. |
O’Byrne, | Wicklow. |
O’Cahaney, | Mayo. |
O’Cahill, | Carlow, Clare, Galway, Kerry, Tipperary. |
O’Callaghan, | Clare, Cork, Mayo. Tipperary. |
O’Callan, | Armagh, Kilkenny |
O’Callanan, | Cork, Galway. |
O’Canavan, | Galway. |
O’Cannanan, | Donegal. |
O’Carberry, | Westmeath. |
O’Carey, | Kildare. |
O’Carmody, | Clare. |
O’Carolan, | Londonderry, Meath. |
O’Carragher, | Louth. |
O’Carroll, | Kerry, Kilkenny, King’s, Leitrim, Louth, Tipperary. |
O’Casey, | Cork, Fermanagh, Kerry, Limerick, Westmeath. |
O’Cashin, | Galway. |
O’Cassidy, | Fermanagh, Londonderry, Monaghan. |
O’Cavanagh, | Carlow, Wexford. |
O’Cawley, | Galway. |
O’Claisin, | Cork. |
O’Clerkin, | Limerick. |
O’Clery, | Cavan, Clare, Donegal, Galway. |
O’Coffey, | Galway, Westmeath. |
O’Coigley, | Donegal, Fermanagh. |
O’Coleman, | Cork, Louth, Sligo. |
O’Colgan, | Armagh, Down, Kildare. |
O’Colman, | Louth. |
O’Coltaran, | Down. |
O’Conaghty, | Cavan, Sligo. |
O’Concannon, | Roscommon. |
O’Conealy, | Galway. |
O’Conlan, | Limerick. |
O’Connegan, | Mayo. |
O’Connelan, | Tyrone. |
O’Connell, | Clare, Down, Galway, Kerry, Limerick. |
O’Connellan, | Galway, Mayo, Roscommon. |
O’Connolly, | Galway, Monaghan. |
O’Connor, | Kildare, Roscommon. |
O’Conolly, | Meath. |
O’Conor, | Clare, Galway, Kerry, King’s, Londonderry, Mayo, Roscommon, Sligo. |
O’Conran, | Waterford. |
O’Considine, | Clare. |
O’Cooney, | Tyrone. |
O’Corcoran, | Fermanagh, Tipperary. |
O’Corley, | Sligo. |
O’Cormac, | Down. |
O’Corr, | Roscommon. |
O’Corran, | Tyrone. |
O’Corrigan, | Fermanagh, Westmeath. |
O’Cosgry, | Wexford. |
O’Cowhy, | Cork. |
O’Coyle, | Cavan, Donegal. |
O’Creagh, | Clare, Cork, Kerry. |
O’Crean, | Sligo. |
O’Criocan, | Tyrone. |
O’Criodan, | Antrim. |
O’Cronin, | Kerry. |
O’Cronly, | Cork. |
O’Crossan, | Tyrone. |
O’Crotty, | Waterford. |
O’Crowly, | Cork. |
O’Cuire, | Tipperary. |
O’Cuirneen, | Leitrim. |
O’Cullen, | Cork, Galway, Kildare, Limerick, Tipperary, Wicklow. |
O’Cullenan, | Clare, Cork, Tipperary. |
O’Culligan, | Clare. |
O’Cummin, | Mayo. |
O’Curran, | Clare, Donegal. |
O’Curry, | Cavan, Cork, Westmeath. |
O’Daly, | Cavan, Clare, Cork, Galway, Kerry, Westmeath. |
O’Danaher, | Cork. |
O’Davoren, | Clare. |
O’Dea, | Clare, Cork, Tipperary. |
O’Deasey, | Cork. |
O’Deegan, | Clare. |
O’Delany, | Kerry, Kilkenny. |
O’Dempsey, | Kildare, King’s, Queen’s. |
O’Dennehy, | Waterford. |
O’Dennery, | Cork. |
O’Dermody, | Clare, Tipperary. |
O’Devin, | Fermanagh. |
O’Devir, | Donegal. |
O’Devlin, | Londonderry, Sligo |
O’Dinan, | Tipperary. |
O’Dinane, | Cork. |
O’Dineen, | Cork. |
O’Dinerty, | Tipperary. |
O’Dinnahan, | Limerick. |
O’Dogherty, | Donegal, Mayo. |
O’Dolan, | Cavan, Mayo. |
O’Donaghey, | Galway. |
O’Donegan, | Cork. |
O’Donelly, | Donegal. |
O’Donevan, | Limerick. |
O’Donlevy, | Donegal, Down, Tyrone. |
O’Donnegan, | Armagh, Fermanagh, Tipperary, Tyrone. |
O’Donnelan, | Roscommon. |
O’Donnell, | Donegal, Galway, Mayo, Sligo. |
O’Donnellan, | Antrim, Galway. |
O’Donnelly, | Tipperary, Tyrone. |
O’Donoghoe, | Kerry, Kilkenny. |
O’Donohoe, | Tipperary. |
O’Donovan, | Cork, Limerick. |
O’Dooley, | Westmeath. |
O’Doolin, | Kerry. |
O’Dooyarma, | Donegal. |
O’Doran, | Queen’s, Wexford. |
O’Dorchy, | Mayo. |
O’Dornin, | Donegal. |
O’Dorrian, | Donegal. |
O’Dowd, | Mayo, Sligo. |
O’Dowling, | Queen’s, Wicklow. |
O’Doyle, | Carlow, Galway, Kilkenny, Wexford, Wicklow. |
O’Doyne, | Carlow. |
O’Dreenan, | Galway. |
O’Drinan, | Clare. |
O’Driscoll, | Cork. |
O’Drom, | Cavan. |
O’Duane, | Galway. |
O’Duff, | Queen’s. |
O’Duffy, | Donegal, Galway, Mayo, Monaghan. |
O’Dugan, | Cork, Mayo, Roscommon, Wexford. |
O’Duigenan, | Roscommon. |
O’Dunn, | Kildare, Meath, Queen’s. |
O’Dunnady, | Kerry. |
O’Durkan, | Sligo. |
O’Duvan, | Meath. |
O’Duvany, | Armagh, Tyrone. |
O’Dwyer, | Tipperary. |
O’Eire, | Antrim. |
O’Etigan, | Tyrone. |
O’Fahy, | Galway. |
O’Fallon, | Roscommon. |
O’Falvey, | Cork, Kerry. |
O’Farrelly, | Cavan. |
O’Fay, | Westmeath. |
O’Feenaghty, | Kerry, Roscommon. |
O’Feeney, | Galway, Sligo. |
O’Felan, | Fermanagh, Waterford. |
O’Ferral, | Longford. |
O’Fihelly, | Cork, Roscommon. |
O’Finan, | Mayo. |
O’Finegan, | Mayo, Roscommon. |
O’Finn, | Leitrim. |
O’Finnelan, | Westmeath. |
O’Flahavan, | Waterford. |
O’Flaherty, | Galway. |
O’Flanagan, | Fermanagh. |
O’Flannagan, | Roscommon, Waterford. |
O’Flannelly, | Sligo. |
O’Flannery, | Limerick, Mayo. |
O’Flattery, | Clare. |
O’Florry, | Down. |
O’Flynn, | Antrim, Cork, Kerry, Mayo, Roscommon. |
O’Fogarty, | Tipperary. |
O’Foley, | Kerry. |
O’Foran, | Galway. |
O’Forranan, | Donegal. |
O’Fox, | Longford, Meath. |
O’Freel, | Donegal, Londonderry. |
O’Furey, | Tipperary. |
O’Furry, | Antrim. |
O’Fynn, | Clare. |
O’Gahan, | Wicklow. |
O’Gallagher, | Donegal. |
O’Gallivan, | Kerry. |
O’Gara, | Sligo. |
O’Garvey, | Armagh, Down, Wexford. |
O’Gavagan, | Mayo, Sligo. |
O’Gearan, | Mayo. |
O’Geary, | Waterford. |
O’Gevany, | Galway. |
O’Gleeson, | Tipperary. |
O’Glennon, | Roscommon. |
O’Gloran, | Kilkenny. |
O’Gogarty, | Meath. |
O’Gorman, | Carlow, Clare, Fermanagh. |
O’Gormley, | Donegal, Mayo. |
O’Gormoge, | Mayo. |
O’Grady, | Clare, Kerry, Limerick, Mayo. |
O’Griffin, | Clare, Kerry. |
O’Hagarty, | Kerry, Londonderry. |
O’Hagerty, | Donegal. |
O’Halahan, | Cork. |
O’Halligan, | Meath. |
O’Hallinan, | Limerick. |
O’Halloran, | Clare, Galway. |
O’Hamill, | Antrim, Tyrone. |
O’Hand, | Meath. |
O’Hanley, | Roscommon. |
O’Hanlon, | Armagh. |
O’Hanrahan, | Westmeath. |
O’Hanratty, | Armagh. |
O’Hanvey, | Down, Westmeath. |
O’Hara, | Antrim, Londonderry, Mayo, Sligo. |
O’Harkan, | Donegal. |
O’Harney, | Kerry. |
O’Hart, | Meath, Sligo. |
O’Hartigan, | Cork, Limerick. |
O’Haverty, | Galway, |
O’Hea, | Cork, Limerick, Meath. |
O’Healy, | Cork, Kerry. |
O’Heaney, | Fermanagh. |
O’Heffernan, | Clare, Tipperary. |
O’Hehir, | Clare. |
O’Heir, | Armagh. |
O’Hely, | Kilkenny, Limerick. |
O’Hennesey, | King’s, Westmeath. |
O’Hennigan, | Cork. |
O’Heoghy, or Hoey, | Down. |
O’Herlihy, | Cork. |
O’Heyne, | Clare, Cork, Galway. |
O’Hickey, | Clare, Tipperary. |
O’Higgin, | Longford, Mayo, Westmeath. |
O’Hoey, | Monaghan. |
O’Hogan, | Clare, Tipperary. |
O’Honan, | Limerick. |
O’Honeen, | Clare. |
O’Hoolaghan, | Cork, King’s. |
O’Hoollaghan, | Galway. |
O’Horan, | Galway, Wicklow. |
O’Horgan, | Cork. |
O’Hosey, | Fermanagh, Tyrone. |
O’Howley, | Clare, Sligo. |
O’Hugh, | Donegal. |
O’Hurley, | Cork, Limerick, Tipperary. |
O’Hynes, | Galway. |
O’Kane, | Antrim, Londonderry. |
O’Kean, | Galway, Tipperary. |
O’Kearney, | Clare, King’s, Tipperary, Westmeath. |
O’Kearny, | Cork, Mayo. |
O’Keefe, | Cork. |
O’Keeley, | Clare. |
O’Keely, | Kilkenny, Tipperary. |
O’Keenan, | Fermanagh, Londonderry. |
O’Keerin, | Mayo. |
O’Keevan, | Antrim, Sligo. |
O’Keiran, | Armagh. |
O’Kelleher, | Cork, Kerry, Tipperary. |
O’Kelly, | Down, Dublin, Galway, Kildare, Louth, Meath, Queen’s, Roscommon, Tyrone, Wicklow. |
O’Kennedy, | Kerry, Tipperary. |
O’Kenny, | Donegal, Roscommon. |
O’Kernaghan, | Donegal, Sligo. |
O’Kerrigan, | Mayo. |
O’Keveny, | Kilkenny. |
O’Killeen, | Mayo. |
O’Kindellan, | Meath. |
O’Kinealy, | Limerick. |
O’Kinsellagh, | Carlow. |
O’Kirwan, | Galway. |
O’Kirwick, | Limerick. |
O’Kissane, | Kerry. |
O’Lanigan, | Tipperary. |
O’Largnan, | Down. |
O’Larkin, | Armagh, Galway, Wexford. |
O’Larrisey, | Mayo. |
O’Laverty, | Donegal, Tyrone. |
O’Lavett, | Mayo. |
O’Lawlor, | Down, Queen’s. |
O’Lawry, | Down. |
O’Leahan, | Galway. |
O’Leahy, | Kerry. |
O’Leaney, | Donegal. |
O’Leary, | Cork. |
O’Lee, | Galway. |
O’Lehan or Lyons, | Cork. |
O’Lenahan, | Tipperary. |
O’Lennon, | Galway, Mayo. |
O’Leyne, | Kerry. |
O’Liddy, | Clare. |
O’Loan, | Tyrone. |
O’Loghlin, | Clare. |
O’Loman, | Galway, Roscommon. |
O’Lomasey, | Cork. |
O’Lonergan, | Roscommon, Tipperary. |
O’Longan, | Down. |
O’Looney, | Cork. |
O’Loughnan, | Down, Kilkenny, Mayo. |
O’Luinin, | Fermanagh. |
O’Lunney, | Tyrone. |
O’Lynch, | Cavan, Clare, Cork, Down, Tipperary. |
O’Lynchy, | Donegal. |
O’Macken, | Down. |
O’Mackesey, | Limerick. |
O’Mackey, | Tipperary. |
O’Madden, | Galway, King’s. |
O’Maginn, | Galway. |
O’Mahon, | Down. |
O’Mahony, | Cork, Kerry. |
O’Malbride, | Roscommon. |
O’Malley, | Mayo. |
O’Malone, | Westmeath. |
O’Malquiney, | Tipperary. |
O’Manning, | Galway. |
O’MaolConry, | Roscommon. |
O’Markey, | Louth. |
O’Marron, | Armagh, Monaghan. |
O’Meagher, | Tipperary. |
O’Meaney, | Roscommon. |
O’Meara, | Tipperary. |
O’Meechan, | Leitrim. |
O’Meehan, | Fermanagh, Sligo, Tipperary. |
O’Melaghlin, | Meath, Westmeath. |
O’Mellan, | Tyrone. |
O’Milford, | Mayo. |
O’Moghan, | Mayo. |
O’Molloy, | King’s. |
O’Moloney, | Clare. |
O’Monahan, | Roscommon. |
O’Mongan, | Sligo. |
O’Mooney, | King’s, Queen’s. |
O’Moore, | Down, Kerry, Queen’s. |
O’Moran, | Down, Galway, Kerry, Mayo, Roscommon, Sligo. |
O’Moriarty, | Kerry. |
O’Morony, | Clare, Cork, Limerick. |
O’Morrison, | Donegal, Sligo. |
O’Morrissey, | Sligo, Tipperary. |
O’Moynagh, | Sligo. |
O’Mulcahy, | Limerick, Tipperary. |
O’Mulclohy, | Sligo. |
O’Muldoon, | Fermanagh. |
O’Muldorry, | Donegal. |
O’Mulfinny, | Longford. |
O’Mulgee, | Donegal. |
O’Mulhall, | Queen’s. |
O’Mulhollan, | Londonderry. |
O’Mulholland, | Antrim. |
O’Mulkerrin, | Galway. |
O’Mullally, | Galway. |
O’Mullane, | Cork, Kerry. |
O’Mullany, | Sligo, Waterford. |
O’Mullarky, | Galway. |
O’Mulledy, | Westmeath. |
O’Mulleeny, | Mayo. |
O’Mullen, | Londonderry. |
O’Mulligan, | Cavan, Londonderry. |
O’Mullins, | Clare. |
O’Mulloy, | Roscommon. |
O’Mulmoghery or Early | Donegal. |
O’Mulrenin, | Mayo, Roscommon. |
O’Mulrooney, | Fermanagh, Galway. |
O’Mulroy, | Mayo. |
O’Mulvany, | Donegal, King’s, Sligo. |
O’Mulvey, | Leitrim. |
O’Mulvihil, | Roscommon. |
O’Muready, | King’s. |
O’Murphy, | Cork, Wexford. |
O’Murray, | Cavan, Donegal, Londonderry, Mayo. |
O’Murrigan, | Kildare. |
O’Murtagh, | Meath. |
O’Naghtan or Norton. | Galway. |
O’Neil, or Nihil, | Clare. |
O’Neill, | Antrim, Armagh, Donegal, Down, Tyrone. |
O’Neney, | Tyrone. |
O’Neny, | Monaghan. |
O’Neylan, | Armagh, Clare. |
O’Nolan, | Carlow. |
O’Noonan, | Cork. |
O’Norton, | Roscommon. |
O’Quigly, | Londonderry. |
O’Quill, | Kerry. |
O’Quinlan, | Kerry, Tipperary. |
O’Quinlevan, | Clare, Tipperary. |
O’Quinn, | Clare, Donegal, Limerick, Londonderry, Longford, Mayo, Tyrone. |
O’Rafferty, | Donegal, Tyrone. |
O’Regan, | Cork, Meath, Queen’s. |
O’Reilly, | Cavan, Longford, Meath, Westmeath. |
O’Riordan, | Cork. |
O’Roddan, | Mayo. |
O’Roddy, | Donegal. |
O’Rodoghan, | Leitrim. |
O’Rogan, | Down. |
O’Ronan, | Longford, Mayo. |
O’Ronayne, | Cork. |
O’Rooney, | Down. |
O’Rory, | Meath. |
O’Rothlan, | Mayo. |
O’Rourke, | Leitrim. |
O’Ryan, | Carlow, Kilkenny, Limerick, Tipperary. |
O’Scanlan, | Kerry, Limerick. |
O’Scanlon, | Louth. |
O’Scannell, | Cork. |
O’Scullan, | Londonderry. |
O’Scully, | Tipperary, Westmeath. |
O’Scurry, | Galway. |
O’Sexton, | Tipperary. |
O’Shanahan, | Tipperary. |
O’Shaughnessy, | Clare, Galway. |
O’Shea, | Cork, Kerry, Kilkenny, Tipperary. |
O’Sheehan, | Galway, Kerry, Limerick. |
O’Sheeran, | Donegal. |
O’Sheridan, | Cavan, Longford. |
O’Shiel, | Antrim, Westmeath. |
O’Sionagh, or Fox, | King’s. |
O’Slattery, | Kerry, Tipperary. |
O’Slevin, | Longford. |
O’Spillan, | Tipperary. |
O’Spillane, | Sligo. |
O’Sullivan, | Cork, Galway, Kerry, Tipperary. |
O’Talcharan, | Mayo. |
O’Tarcert, | Donegal. |
O’Teige or Tighe, | Wicklow. |
O’Teigue, | Tyrone. |
O’Tierney, | Armagh, Mayo. |
O’Tolarg, | Westmeath. |
O’Tomalty, | Tyrone. |
O’Toole, | Galway, Kildare, Mayo, Wicklow. |
O’Tormey, | Galway. |
O’Tracey, | Galway. |
O’Tracy, | Fermanagh. |
O’Traynor, | Meath. |
O’Tully, | Fermanagh. |
O’Tuohy, | Cork. |
O’Tuomey, | Cork. |