69 Irish Last Names Starting with O’

Central to Ireland’s culture are Irish surnames, particularly those beginning with ‘O”, a prefix indicating lineage. On this page, immerse yourself in historically profound Irish surnames starting with “O’.”

What are Irish Last Names Starting with O’?

Irish surnames that start with ‘O” are reminiscent of a time when names narrated stories, indicated genealogies, and celebrated clans. The prefix ‘O” translates to ‘descendant of’ or ‘grandson of’ in Gaelic, signifying ancestry and family ties. The captivating aspect of Irish surnames prefixed with ‘O” is how they speak of legacies, traditions, and sometimes even professions.

For instance, ‘O’Connor,’ meaning ‘descendant of Conchobhar,’ which translates to ‘lover of hounds,’ and ‘O’Neill,’ meaning ‘descendant of Niall,’ often associated with champions or warriors, are prime examples of these surnames’ depth and significance. Discover a treasure trove of Irish heritage below with surnames that start with ‘O”.

Irish Last Names Starting with O’

Here, we present our list of Irish surnames beginning with ‘O” to embrace the significance and history encapsulated within each name.

1. O’Bear – Descendant of Bearach
2. O’Beirne – Descendant of Bjorn, meaning bear
3. O’Boyle – Descendant of Baoigheallach, meaning profitable pledges
4. Obrien – Descendant of Brian
5. O’Brien – Descendant of Brian
6. O’Byrne – Descendant of Bran, meaning raven
7. O’Cahan – Descendant of Cathán
8. Ocallaghan – Descendant of Ceallachán
9. O’Callaghan – Descendant of Ceallachán, meaning strife
10. O’Carroll – Champion
11. O’Casey – Descendant of Cathasaigh
12. O’Clery – Descendant of Cleirigh
13. Oconnell – Descendant of Conaill
14. O’Connell – Descendant of Conall, meaning strong wolf
15. Oconnor – Descendant of Conchobhar
16. O’Connor – Descendant of Conchobhar, meaning lover of hounds
17. O’Day – Descendant of David
18. O’Dea – Descendant of Deaghaidh
19. O’Doherty – Descendant of Dochartach, meaning obstructive
20. Odonnell – Descendant of Domhnall
21. O’Donnell – Descendant of Domhnall, meaning world ruler
22. O’Donoghue – Descendant of Donnchadh, meaning brown warrior
23. O’Donovan – Descendant of Donndubhán, meaning brown-black
24. O’Dowd – Descendant of Dubhda, meaning dark
25. O’Driscoll – Descendant of the interpreter
26. O’Dwyer – Dark wise one
27. O’Farrell – Descendant of Fearghal, meaning man of valor
28. O’Flaherty – Descendant of the bright, meaning radiant prince
29. O’Flynn – Descendant of Flann, meaning red, meaning ruddy
30. O’Friel – Descendant of Fréil
31. O’Gara – Descendant of Gadhra, meaning hound
32. O’Gorman – Descendant of Gormán, meaning little blue one
33. O’Grady – Descendant of Grádaigh, meaning noble
34. O’Hagan – Descendant of Aodhán, meaning fire
35. O’Halloran – Descendant of Hoolahan, meaning proud
36. O’Hanlon – Descendant of Ó hAnluain, meaning like a hound
37. O’Hara – Descendant of Eaghra, meaning horse lord
38. O’Hare – Descendant of Eaghra, meaning fear
39. O’Hea – Descendant of Aodh
40. O’Higgins – Descendant of Uigin
41. O’Kane – Descendant of Cathán, meaning warrior
42. O’Keefe – Descendant of Caomh, meaning gentle
43. O’Keeffe – Gentle
44. O’Kelly – Descendant of Ceallach, meaning strife, meaning contention
45. Oleary – Descendant of Laoghaire, meaning calf-herder
46. O’Leary – Calf-herder
47. O’Loughlin – Descendant of the Viking
48. O’Lynn – Descendant of Laighin
49. O’Mahoney – Descendant of Mathghamhna, meaning bear
50. Omahony – Descendant of Mathghamhna, meaning bear
51. O’Mahony – Descendant of Mathghamhna, meaning bear
52. O’Malley – Descendant of a follower of Saint John
53. O’Mara – Descendant of the sea
54. O’Meara – Descendant of Meadhair
55. O’Neal – Descendant of Niall
56. Oneill – Descendant of Niall
57. O’Neill – Descendant of Niall
58. O’Regan – Descendant of Riagán
59. Oreilly – Descendant of Raghallaigh
60. O’Reilly – Outgoing
61. O’Riordan – Royal poet
62. O’Rourke – Descendant of Ruarc
63. O’Shaughnessy – Descendant of Seanach, meaning wise, meaning old
64. Oshea – Descendant of Seaghdha, meaning fine, meaning stately
65. O’Shea – Hawk-like, fortunate
66. O’Sheehan – Descendant of Siodhacháin
67. Osullivan – Descendant of Súilleabhán
68. O’Sullivan – Descendant of the hawk-eyed
69. O’Toole – Descendant of Tuathal, meaning prince of the people

See more Irish Last Names