A list of Irish surnames beginning with the letter O. Many Irish surnames have a O’ in front in their Irish version, this list is mainly confined to those names where the O’ is commonly used in the English version of the name.
O’Brien
Found in: Clare, Limerick, very widespread.
Origin: Gaelic
Descendents of Brian Boru, High King of Ireland.
O’Callaghan
Variant: Callaghan, Callahan
In Irish: Ó Ceallacháin
Found in: Cork, Limerick, widespread.
Origin: Gaelic
Probably originated from Ceallachan, a 10th century King of Munster.
O’Casey
Variant: Casey
In Irish: O Cathasaigh
Origin: Gaelic
Means “vigilant”.
O’Connell
In Irish: Ó Conaill
Found in: Derry, Galway, Kerry widespread,
Origin: Gaelic
Very old name.
O’Connor
Variant: O’Conor, Conner, Connor
In Irish: Ó Conchobhair,
Found in: Clare, Cork, Kerry, Offaly, Roscommon, widespread.
Origin: Gaelic
Means “hero or champion”; descendents of King Conchobhair of Connacht. .
O’Dea
In Irish: O Deaghaidh
Found in: Clar, Cork, Dublin, Limerick, Tipperary
Origin: Gaelic
O’Donnell
In Irish: Ó Domhnaill
Found in: Donegal.
Origin: Gaelic
Means “world mighty”
O’Donovan
In Irish: Ó Donnabhain
Found in: Cork, Kilkenny
Origin: Gaelic
Two colours in the name: donn meaning “brown” and dubhann “black”.
O’Dowd
Variant: Dodd, Doody, Duddy
In Irish: O Dubhda
Found in: Galway, Mayo, Sligo
Origin: Gaelic
Means “black”.
O’Driscoll
Variant: Driscoll.
In Irish: O hEidersceoil
Found in: Cork
Origin: Gaelic
Means “go between or interpreter”.
O’Dwyer
Variant: Dwyer
In Irish: O Dubhuidir,
Found in: Mayo, Sligo.
Origin: Gaelic
Means “black shirt”.
O’Flaherty
Variant: Flaherty, O’Flaverty. O’Laverty
In Irish: Ó Flaithbheartaigh
Found in: Galway, Mayo
Origin: Gaelic
Very ancient family
O’Gara
In Irish: O Gadhra
Found in: Cavan, Mayo, Sligo.
Origin: Gaelic
Gadhra means “a mastiff ” or “dog”
O’Gorman
Variant: Gorman, Grimes
In Irish: O Gormain
Found in: Clare, Laois, Monaghan.
Origin: Gaelic
O’Grady
Variant: Grady
In Irish: Ó Grádaigh
Found in: Clare, Galway, Limerick.
Origin: Gaelic
Means “illustrious”; part of the Dalcassian sept and so related to the O’Briens.
O’Hagan
Variant: Hagan, Aiken
In Irish: O hAodhagain. Ó hAgain,
Found in: Tyrone, Ulster
Origin: Gaelic
Means “young”.
O’Halloran
Variant: Halloran
In Irish: O hAllmhurain
Found in: Clare, Galway.
Origin: Gaelic
Means “stranger from over the sea”.
O’Hara
In Irish: O hEaghra
Found in: Antrim, Sligo
Origin: Gaelic
O’Hegarty
Variant: Hegerty, Hagerty
In Irish: O hEigceartaigh
Found in: Cork, Derry, Donegal.
Origin: Gaelic
Means “unjust”
O’Higgins
In Irish: O hUigin
Found in: Sligo, Clare, Galway, widespread.
Origin: Gaelic
Means “knowledge or ingenuity”.
O’Keeffe
Variant: O’Keefe
In Irish: Ó Caoinmh
Found in: Cork, Limerick
Origin: Gaelic
Caom means “noble” or “gentle”. Also means “descendent of Caoinmh”, himeself son of Fionghuine, a King of Munster.
O’Leary
Variant: Leary
In Irish: O Laoghaire
Found in: Cork
Origin: Gaelic
Means “calf keeper”
O’Malley
Variant: Melia
In Irish: Ó Máille
Found in: Mayo
Origin: Gaelic
Old and distinguished family. The name is derived from “maglios” an ancient Celtic word meaning “chief”.
O’Meara
Variant: Meara, O’Mara, Mara
In Irish: O Meadhra,
Found in: Tipperary, widespread.
Origin: Gaelic
Means “mirth”.
O’Neill
Variant: Neill, Nihill
Found in: Antrim, Down, Tyrone, widespread.
Origin: Gaelic
Very old and prestigious family. Neill means “champion”.
O’Reilly
Variant: Reilly, Riley, O’Rahilly
In Irish: Ó Raghailligh
Found in: Cavan, widespread
Origin: Gaelic
Ragheallach means “gregarious race”
O’Riordan
Variant: Riordan, Reardon.
In Irish: O Riordáin
Found in: Cork, Tipperary.
Origin: Gaelic
Means “royal bard”.
O’Rourke
Variant: Roark, Rooke, Rourke, Rorke
In Irish: Ó Ruairc
Found in: Cavan, Leitrim.
Origin: Norse
Originates from the Norse-Viking name Hrothrekr, who married into the Irish.
O’Shaughnessy
Variant: Shaughnessy
In Irish: O Seachnsaigh
Found in: Clare, Galway, Limerick.
Origin: Gaelic
O’Shea
Variant: Shea, Shee
In Irish: Ó Séaghdha, Ó Sé
Found in: Kerry, Kilkenny.
Origin: Gaelic
Means “stately or majestic” and also “dauntless”. One of the merchant families of Kilkenny.
O’Sullivan
Variant: Sullivan
In Irish: Ó Súileabháin
Found in: Cork, Kerry, Tipperary.
Origin: Gaelic
Means “one-eyed” or “hawk-eyed”.
O’Toole
Variant: Toal, Tool, Toole, Toohill, Twohill.
In Irish: Ó Tuathail
Found in: Kildare, Wicklow, widespread.
Origin: Gaelic
Descendents of Tuathal, a 10th century King of Leinster. Means “mighty or prosperous people”
10 Comments
My grandmothers maiden name was O’Philemy from the Strabane area, I think. They came to Scotland in about 1900. O’Philemy is not on your list. I’d like to know more about the name and most likely associated places. Can you help me, please?
What does the letter “O ” stand for before surnames( what does it mean) thanks
I cannot find mention my late grandmother’s surname which was O’Hore, not sure of the spelling though. Can you help please.
Why do you listings just go to the letter ‘O’ where are all the names from P to Z/ … in my case ‘S’
Hi.
I have looked at your list of surnames,but I can’t find mine,Mulvey. My father was Irish from Tipperary,so I Am presuming it was an Irish surname,appreciate it if you had any information at all about its origins.
Regards
S Mulvey.
It is indeed an Irish surname, and not an uncommon one. I don’t know a lot about it, but it is a name of Gaelic origin, in Irish it would be Ó Maoilmhiadhaigh – which I bet looks kind of unpronounceable! ‘Mwale (rhymes with ale) – vade- ig’ would be there or thereabouts. I see from a quick search online that there is a general consensus that the comes from the Irish ‘Maidach, meaning honourable. I kind of don’t think that’s quite right. My Irish isn’t brilliant, but I’ve not heard that word – which definitely doesn’t mean it does not exist! Maybe it’s old Irish, or maybe just unknown to me.
The fist part ‘Maoil’ means ‘follower of’, so I’d be inclined to go for the second part as being a person’s name, a leader of some kind. Maybe his name meant honourable, or perhaps he was an honourable person and that’s where this came from.
I notice you have Dwyer/O’Dwyer name coming from Mayo/Sligo but it is from Kilnamanagh in Tipperary. I am a Dwyer from this part of the country. The biggest number of Dwyer/O’Dwyer (900+) families currently live there. This is where the Dwyer/O’Dwyer castles are also located, which were destroyed during the Cromwellian settlements.
My last name is Driotes, some how it has been deformed, according to our family records, our grand grand father came from Europe so the last known last name was Driottiz or Driotez somebody can help me?
Our name in the Gaelic was originally O’ Faodhagain. Translates into Fagan here. Somewhere along the line it changed to the “Figgins” of today. Please, where do I start research on the name? Are there websites, books or libraries in Ireland that you could recommend? Thank you.
I notice with some dismsy that O’Haire is not listed! I can only presume that it si a derivation of another. In gaelic it is Mac an Aodhaoire son of shepherd! How did it become O’Haire
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