Irish Last Names with O: A Comprehensive Guide

Are you looking for an Irish last name that starts with "O"? Look no further! This comprehensive guide will delve into the fascinating world of Irish surnames with the prefix "O", exploring their origins, meanings, and historical significance. From common names like O'Brien and O'Connell to less familiar ones like O'Hanrahan and O'Molloy, this list provides a detailed breakdown of over 40 Irish surnames starting with "O". Discover the rich tapestry of Irish history and cultural heritage embedded within these names, and find the perfect Irish surname for yourself or your loved ones.
1. **O'Brien**: This prominent Irish surname is derived from "Ó Briain," meaning "descendant of Brian," referring to Brian Boru, the legendary High King of Ireland.
2. **O'Connell**: Meaning "descendant of Connell," this surname is connected to the Gaelic clan Ó Conchobhair, prominent in County Galway and beyond.
3. **O'Connor**: Derived from "Ó Conchobhair," meaning "descendant of Conchobhair," this name is associated with the powerful O'Connor dynasty, one of the most influential families in Irish history.
4. **O'Neill**: Meaning "descendant of Niall," this surname traces its roots back to the legendary Niall of the Nine Hostages, a legendary Irish High King.
5. **O'Reilly**: Derived from "Ó Raghallaigh," meaning "descendant of Raghallach," this surname is linked to the powerful O'Reilly clan, prominent in County Cavan.
6. **O'Sullivan**: Meaning "descendant of Suibhne," this surname is connected to the Gaelic clan Ó Súilleabháin, prominent in County Kerry.
7. **O'Doherty**: Derived from "Ó Dochartaigh," meaning "descendant of Dochartach," this surname is linked to the Gaelic clan Ó Dochartaigh, prominent in County Donegal.
8. **O'Callaghan**: Meaning "descendant of Callaghan," this surname is associated with the Gaelic clan Ó Callanáin, prominent in County Cork.
9. **O'Carroll**: Derived from "Ó Cearbhaill," meaning "descendant of Cearbhall," this surname is linked to the Gaelic clan Ó Cearbhaill, prominent in County Offaly.
10. **O'Shea**: Meaning "descendant of Shea," this surname is connected to the Gaelic clan Ó Séaghdha, prominent in County Kerry.
11. **O'Malley**: Derived from "Ó Maolalaidh," meaning "descendant of Maolalaidh," this surname is linked to the Gaelic clan Ó Maolalaidh, prominent in County Galway.
12. **O'Toole**: Meaning "descendant of Tuathal," this surname is connected to the Gaelic clan Ó Tuathail, prominent in County Wicklow.
13. **O'Flaherty**: Derived from "Ó Flaitheartaigh," meaning "descendant of Flaithbheartach," this surname is linked to the Gaelic clan Ó Flaitheartaigh, prominent in County Galway.
14. **O'Moore**: Meaning "descendant of Muircheartach," this surname is connected to the Gaelic clan Ó Muireadhaigh, prominent in County Laois.
15. **O'Grady**: Derived from "Ó Grádaigh," meaning "descendant of Grádagh," this surname is linked to the Gaelic clan Ó Grádaigh, prominent in County Limerick.
16. **O'Donovan**: Meaning "descendant of Domhnall," this surname is connected to the Gaelic clan Ó Donabháin, prominent in County Cork.
17. **O'Hanrahan**: Derived from "Ó hAnrachain," meaning "descendant of Anrachain," this surname is linked to the Gaelic clan Ó hAnrachain, prominent in County Tipperary.
18. **O'Dwyer**: Meaning "descendant of Dubhghlas," this surname is connected to the Gaelic clan Ó Dubhdaigh, prominent in County Tipperary.
19. **O'Rourke**: Derived from "Ó Ruairc," meaning "descendant of Ruairc," this surname is linked to the Gaelic clan Ó Ruairc, prominent in County Leitrim.
20. **O'Nolan**: Meaning "descendant of Niallán," this surname is connected to the Gaelic clan Ó Nualláin, prominent in County Kildare.
21. **O'Mahony**: Derived from "Ó Mathúna," meaning "descendant of Mathúna," this surname is linked to the Gaelic clan Ó Mathúna, prominent in County Cork.
22. **O'Higgins**: Meaning "descendant of Ó hUiginn," this surname is connected to the Gaelic clan Ó hUiginn, prominent in County Westmeath.
23. **O'Brien**: Meaning "descendant of Briain," this surname is associated with the Gaelic clan Ó Briain, prominent in County Clare.
24. **O'Daly**: Derived from "Ó Dálaigh," meaning "descendant of Dálach," this surname is linked to the Gaelic clan Ó Dálaigh, prominent in County Kerry.
25. **O'Loughlin**: Meaning "descendant of Lochlainn," this surname is connected to the Gaelic clan Ó Lochlainn, prominent in County Monaghan.
26. **O'Kelly**: Derived from "Ó Ceallaigh," meaning "descendant of Ceallach," this surname is linked to the Gaelic clan Ó Ceallaigh, prominent in County Galway.
27. **O'Connor**: Meaning "descendant of Conchobhair," this surname is associated with the Gaelic clan Ó Conchobhair, prominent in County Roscommon.
28. **O'Neill**: Meaning "descendant of Niall," this surname traces its roots back to the legendary Niall of the Nine Hostages, a legendary Irish High King.
29. **O'Reilly**: Derived from "Ó Raghallaigh," meaning "descendant of Raghallach," this surname is linked to the powerful O'Reilly clan, prominent in County Cavan.
30. **O'Sullivan**: Meaning "descendant of Suibhne," this surname is connected to the Gaelic clan Ó Súilleabháin, prominent in County Kerry.
31. **O'Doherty**: Derived from "Ó Dochartaigh," meaning "descendant of Dochartach," this surname is linked to the Gaelic clan Ó Dochartaigh, prominent in County Donegal.
32. **O'Callaghan**: Meaning "descendant of Callaghan," this surname is associated with the Gaelic clan Ó Callanáin, prominent in County Cork.
33. **O'Carroll**: Derived from "Ó Cearbhaill," meaning "descendant of Cearbhall," this surname is linked to the Gaelic clan Ó Cearbhaill, prominent in County Offaly.
34. **O'Shea**: Meaning "descendant of Shea," this surname is connected to the Gaelic clan Ó Séaghdha, prominent in County Kerry.
35. **O'Malley**: Derived from "Ó Maolalaidh," meaning "descendant of Maolalaidh," this surname is linked to the Gaelic clan Ó Maolalaidh, prominent in County Galway.
36. **O'Toole**: Meaning "descendant of Tuathal," this surname is connected to the Gaelic clan Ó Tuathail, prominent in County Wicklow.
37. **O'Flaherty**: Derived from "Ó Flaitheartaigh," meaning "descendant of Flaithbheartach," this surname is linked to the Gaelic clan Ó Flaitheartaigh, prominent in County Galway.
38. **O'Moore**: Meaning "descendant of Muircheartach," this surname is connected to the Gaelic clan Ó Muireadhaigh, prominent in County Laois.
39. **O'Grady**: Derived from "Ó Grádaigh," meaning "descendant of Grádagh," this surname is linked to the Gaelic clan Ó Grádaigh, prominent in County Limerick.
40. **O'Donovan**: Meaning "descendant of Domhnall," this surname is connected to the Gaelic clan Ó Donabháin, prominent in County Cork.
41. **O'Hanrahan**: Derived from "Ó hAnrachain," meaning "descendant of Anrachain," this surname is linked to the Gaelic clan Ó hAnrachain, prominent in County Tipperary.
42. **O'Dwyer**: Meaning "descendant of Dubhghlas," this surname is connected to the Gaelic clan Ó Dubhdaigh, prominent in County Tipperary.
43. **O'Rourke**: Derived from "Ó Ruairc," meaning "descendant of Ruairc," this surname is linked to the Gaelic clan Ó Ruairc, prominent in County Leitrim.
44. **O'Nolan**: Meaning "descendant of Niallán," this surname is connected to the Gaelic clan Ó Nualláin, prominent in County Kildare.
45. **O'Mahony**: Derived from "Ó Mathúna," meaning "descendant of Mathúna," this surname is linked to the Gaelic clan Ó Mathúna, prominent in County Cork.
46. **O'Higgins**: Meaning "descendant of Ó hUiginn," this surname is connected to the Gaelic clan Ó hUiginn, prominent in County Westmeath.
47. **O'Molloy**: Derived from "Ó Maolmhóid," meaning "descendant of Maolmhóid," this surname is linked to the Gaelic clan Ó Maolmhóid, prominent in County Offaly.
48. **O'Brien**: Meaning "descendant of Briain," this surname is associated with the Gaelic clan Ó Briain, prominent in County Clare.
49. **O'Daly**: Derived from "Ó Dálaigh," meaning "descendant of Dálach," this surname is linked to the Gaelic clan Ó Dálaigh, prominent in County Kerry.
50. **O'Loughlin**: Meaning "descendant of Lochlainn," this surname is connected to the Gaelic clan Ó Lochlainn, prominent in County Monaghan.
51. **O'Kelly**: Derived from "Ó Ceallaigh," meaning "descendant of Ceallach," this surname is linked to the Gaelic clan Ó Ceallaigh, prominent in County Galway.
52. **O'Connor**: Meaning "descendant of Conchobhair," this surname is associated with the Gaelic clan Ó Conchobhair, prominent in County Roscommon.