Irish Last Names
Ireland was one of the first countries in Europe to use hereditary surnames, beginning around the 10th century. Most Irish last names started as Ó (“grandson, descendant of”) or Mac (“son of”) plus an ancestor’s name — so Murphy is really Ó Murchadha, “descendant of the sea warrior.” Under English rule many families dropped the prefix, then reclaimed it during the Gaelic revival, which is why you see both Brien and O’Brien today.
Below are 90 Irish surnames with their meanings, original Irish forms and the counties where each clan was rooted. Looking for first names to go with them? See Irish boy names and Irish girl names, or start at our Irish names guide.
Most common Irish surnames
These surnames top Ireland’s registers and are carried by millions in the Irish diaspora. Compare them with our list of the most common last names in the English-speaking world.
| Surname | Meaning | Irish form |
|---|---|---|
| Murphy | “Sea warrior” | Ó Murchadha |
| Kelly | Possibly “bright-headed” or “strife” | Ó Ceallaigh |
| O’Sullivan | Possibly “dark-eyed” | Ó Súilleabháin |
| Walsh | “Welshman” | Breathnach |
| Smith | “Son of the smith” | Mac Gabhann |
| O’Brien | “Descendant of Brian” (Brian Boru) | Ó Briain |
| Byrne | “Raven” | Ó Broin |
| Ryan | Possibly “little king” | Ó Riain |
| O’Connor | “Descendant of the lover of hounds” | Ó Conchobhair |
| O’Neill | “Descendant of Niall” (champion) | Ó Néill |
| O’Reilly | Possibly “valiant” | Ó Raghallaigh |
| Doyle | “Dark foreigner” (a Viking) | Ó Dubhghaill |
| McCarthy | “Son of the loving one” | Mac Cárthaigh |
| Gallagher | “Foreign helper” | Ó Gallchobhair |
| O’Doherty | Meaning uncertain | Ó Dochartaigh |
Irish surnames beginning with O’
Each O’ name traces back to a real ancestor, often a king or chieftain of the early medieval period.
| Surname | Meaning | Stronghold |
|---|---|---|
| O’Donnell | “World-mighty” | Donegal |
| O’Mahony | “Bear” | Cork |
| O’Callaghan | Possibly “bright-headed” | Cork |
| O’Shea | “Hawk-like, stately” | Kerry |
| O’Keeffe | “Gentle, kind” | Cork |
| O’Driscoll | “Intermediary, messenger” | West Cork |
| O’Rourke | From Ruarc, Norse “famous ruler” | Leitrim |
| O’Hara | Meaning uncertain | Sligo |
| O’Donovan | “Dark brown” | Cork |
| O’Malley | Meaning uncertain; clan of pirate queen Grace O’Malley | Mayo |
| O’Leary | “Calf-herder” | Cork |
| O’Dwyer | “Dark, tawny” | Tipperary |
| O’Toole | “Ruler of the people” | Wicklow |
| O’Flaherty | “Bright or generous ruler” | Galway |
| O’Grady | “Noble” | Clare |
| O’Farrell | “Man of valor” | Longford |
Irish surnames beginning with Mac and Mc
Mac and Mc are the same prefix, not a sign of Irish versus Scottish origin. For the Scottish side of the family, see Scottish last names.
| Surname | Meaning | Stronghold |
|---|---|---|
| MacMahon | “Son of the bear” | Clare, Monaghan |
| McNamara | “Son of the hound of the sea” | Clare |
| McGrath | “Son of grace, prosperity” | Clare, Waterford |
| McLoughlin | “Son of the Viking (Lochlann)” | Donegal, Derry |
| McGuinness | “Son of Aonghus” (one strength) | Down |
| McKenna | “Son of the fire-born” | Monaghan |
| Maguire | “Son of the pale one” | Fermanagh |
| McDermott | “Son of Diarmuid” | Roscommon |
| McCormack | “Son of Cormac” | Longford, Munster |
| McGovern | “Son of the summer-born” | Cavan |
| McCann | “Son of the wolf cub” | Armagh |
| McHugh | “Son of Aodh” (fire) | Galway, Donegal |
| McKeown | “Son of Eoghan” | Antrim, Down |
| McManus | “Son of Maghnus” (great) | Fermanagh, Roscommon |
Norman and Viking surnames in Ireland
The Anglo-Normans who arrived in 1169 famously became “more Irish than the Irish themselves,” and their names are now thoroughly Irish. Vikings left a mark too; see our Viking last names.
| Surname | Meaning | Origin / stronghold |
|---|---|---|
| Fitzgerald | “Son of Gerald” | Norman; Kildare and Desmond |
| Burke | “Fortified hill” | Norman de Burgh; Connacht |
| Power | “Poor” (le Poer) | Norman; Waterford |
| Butler | “Cup-bearer” to the king | Norman; Kilkenny |
| Roche | “Rock” | Norman; Cork, Wexford |
| Barry | From Barry Island, Wales | Cambro-Norman; Cork |
| Joyce | From Breton Iodoc, “lord” | Welsh-Norman; Connemara |
| Costello | “Son of Oisdealbh” (the Norman de Angulo family) | Norman; Mayo |
| Nugent | From Nogent, France | Norman; Westmeath |
| Dillon | Possibly Norman de Lion | Norman; Westmeath |
| Fleming | “Man from Flanders” | Flemish; Meath, Louth |
| Cotter | “Son of Ottar” (Norse) | Viking; Cork |
| Fitzpatrick | “Son of the servant of Patrick” (Mac Giolla Phádraig) | Gaelic with a Norman-style prefix; Laois |
Irish surnames that lost their O’
Many families dropped the O’ or Mac during the 17th–19th centuries. These now usually appear without a prefix.
| Surname | Meaning | Irish form |
|---|---|---|
| Brennan | Possibly “sorrow” | Ó Braonáin |
| Quinn | “Descendant of Conn” (chief) | Ó Cuinn |
| Kennedy | “Helmeted head” | Ó Cinnéide |
| Hogan | “Young” | Ó hÓgáin |
| Duffy | “Dark” | Ó Dubhthaigh |
| Boyle | Possibly “pledge” | Ó Baoill |
| Dunne | “Brown” | Ó Duinn |
| Keane | “Battler” | Ó Catháin |
| Lynch | “Mariner” | Ó Loingsigh |
| Kavanagh | “Follower of Saint Caomhán” | Caomhánach |
| Daly | From <em>dáil</em>, “assembly”; a famous bardic family | Ó Dálaigh |
| Carroll | Possibly “valorous in battle” | Ó Cearbhaill |
| Hayes | “Fire” | Ó hAodha |
| Clarke | “Clerk” | Ó Cléirigh |
| Casey | “Vigilant” | Ó Cathasaigh |
| Nolan | Possibly “noble” or “champion” | Ó Nualláin |
| Brady | Meaning uncertain | Mac Brádaigh |
Irish clan surnames by county
Before emigration scattered them, most Irish clans were tied to a single territory. If your surname is here, the county is a good place to start researching.
| Surname | Meaning | Stronghold |
|---|---|---|
| Moriarty | “Expert navigator” | Kerry |
| Donnelly | “Brown valor” | Tyrone |
| Hennessy | “Descendant of Aonghus” | Cork |
| Cullen | “Holly” | Wicklow |
| Madden | “Little hound” | Galway |
| Kinsella | Meaning uncertain; from a Leinster royal line | Wexford |
| Mulligan | “Little tonsured one” | Donegal, Monaghan |
| Flanagan | “Red, ruddy” | Roscommon |
| Rafferty | “Prosperity wielder” | Donegal, Sligo |
| Tierney | “Lord” | Mayo |
| Egan | “Son of little fire” | Galway, Tipperary |
| Coughlan | “Cape, hood” | Cork |
| Sweeney | “Pleasant” | Donegal |
| Kearney | “Victorious” | Mayo, Clare |
| Delaney | “Dark challenger” | Laois |
Tips for researching your Irish surname
- Try every spelling. Clerks wrote names as they heard them: O’Sullivan, Sullivan and Sullavan may all be the same family.
- Mac and Mc are interchangeable. Don’t rule out a record because it says McMahon instead of MacMahon.
- Find the county. Because most clans were local, the county where a surname clusters (see Edward MacLysaght’s classic Surnames of Ireland) narrows your search dramatically.
- Check Catholic parish registers. They’re usually the best Irish records before 1864, when civil birth registration began for everyone.
- Look at the neighbors. Welsh, Scottish and English surnames arrived with settlers; our British last names page covers many you’ll meet in Irish records.
Frequently asked questions
What is the most common Irish last name?
Murphy is the most common surname in Ireland, followed by Kelly, O’Sullivan, Walsh, Smith and O’Brien.
What is the difference between Mac and O’ in Irish surnames?
Mac means “son of,” while Ó (O’) means “grandson” or “descendant of.” Both point to a named ancestor; O’ surnames tend to be slightly older.
Is Mc Irish or Scottish?
Both. Mc is simply an abbreviation of Mac, and both spellings are used in Ireland and Scotland. The spelling doesn’t reveal which country a family came from.
Why did Irish people drop the O’ from their names?
From the 1600s onward, English rule and social pressure encouraged anglicized names, so many families dropped O’ and Mac. Some reclaimed them during the Gaelic revival of the late 19th and early 20th centuries.
Are Fitzgerald and Burke Irish names?
They arrived with the Anglo-Normans in the 12th century, but after 850 years in Ireland they are considered fully Irish. “Fitz” is from Norman French fils, “son.”