Ireland was one of the first countries to adopt hereditary surnames. Many of these names were devised during the reign of Brian Boru, the High King of Ireland who fell defending Ireland from the Vikings at the Battle of Clontarf in 1014 AD.
50 Common Irish Surnames
Many of these early Irish surnames began as patronyms to identify a son separately from his father or a grandson from his grandfather. This is why it is very common to see prefixes attached to Irish surnames. Mac, sometimes written Mc, is the Gaelic word for "son" and was attached to the father's name or trade. O is a word all by itself, signifying "grandson" when attached to a grandfather's name or trade.
The apostrophe that usually follows the O actually comes from a misunderstanding by English-speaking clerks in Elizabethan time, who interpreted it as a form of the word "of." Another common Irish prefix, Fitz, derives from the French word fils, also meaning "son."
Brennan
This Irish family was very widespread, settling in Fermanagh, Galway, Kerry, Kilkenny, and Westmeath. The Brennan surname in Ireland is now mostly found in County Sligo and the province of Leinster.
Brown or Browne
Common in both England and Ireland, the Irish Brown families are most commonly found in the province of Connacht (specifically Galway and Mayo), as well as Kerry.
Boyle
The O Boyles were chieftains in Donegal, ruling west Ulster with the O Donnells and the O Doughertys. Boyle descendants can also be found in Kildare and Offaly.
Burke
The Norman last name Burke originated from the borough of Caen in Normandy (de burg means "of the borough"). The Burkes have been in Ireland since the 12th century, settling mainly in the province of Connacht.
Byrne
The O Byrne (Ó Broin) family originally came from Kildare, until the Anglo-Normans arrived and they were driven south to the Wicklow mountains. The Byrne surname is still very common in Wicklow, as well as Dublin and Louth.
Callaghan
The Callaghans were a powerful family in the province of Munster. Individuals with the Irish surname Callaghan (also spelled Callahan) are most numerous in Clare and Cork.
Campbell
Campbell families are very prevalent in Donegal (most are descended from Scottish mercenary soldiers), as well as in Cavan. Campbell is a descriptive surname meaning "crooked mouth."
Carroll
The Carroll surname(and variants such as O'Carroll) can be found throughout Ireland, including Armagh, Down, Fermanagh, Kerry, Kilkenny, Leitrim, Louth, Monaghan, and Offaly. There is also a MacCarroll family (anglicized to MacCarvill) from the province of Ulster.
Clarke
One of the oldest surnames in Ireland, the O Clery surname (anglicized to Clarke) is most prevalent in Cavan.
Collins
The common Irish surname Collins originated in Limerick, though after the Norman invasion they fled to Cork. There are also Collin families from the province of Ulster, most of whom were probably English.
Connell
Three distinct O Connell clans, located in the provinces of Connacht, Ulster, and Munster, are the originators of many of the Connell families in Clare, Galway, Kerry.
Connolly
Originally an Irish clan from Galway, the Connolly families settled in Cork, Meath, and Monaghan.
Connor
In Irish Ó Conchobhair or Ó Conchúir, the Connor last name means "hero or champion." The O Connor family was one of three royal Irish families; they are from Clare, Derry, Galway, Kerry, Offaly, Roscommon, Sligo and the province of Ulster.
Daly
The Irish Ó Dálaigh comes from dáil, meaning a place of assembly. Individuals with the Daly surname hail primarily from Clare, Cork, Galway, and Westmeath.
Doherty
The name in Irish (Ó Dochartaigh) means obstructive or hurtful. In the 4th century, the Dohertys settled around the Inishowen peninsula in Donegal, where they've primarily stayed. The Doherty surname is the most common in Derry. Also spelled Dougherty and Daugherty.
Doyle
The Doyle last name comes from dubh ghall, the "dark foreigner," and is thought to be Norse in origin. In the province of Ulster, they were known as Mac Dubghaill (MacDowell and MacDuggall). The greatest concentration of Doyles is in Leinster, Roscommon, Wexford, and Wicklow.
Duffy
Ó Dubhthaigh, anglicized to Duffy, comes from an Irish name meaning black or swarthy. Their original homeland was Monaghan, where their surname is still the most common. They are also from Donegal and Roscommon.
Dunne
From the Irish for brown (donn), the original Irish name Ó Duinn has by now lost the O prefix. In the province of Ulster, the final e is omitted. Dunne is the most common surname in Laois, where the family originated. Also occasionally spelled Donne.
Farrell
The O Farrell chieftains were lords of Annaly near Longford and Westmeath. Farrell is a surname generally meaning "valiant warrior."
Fitzgerald
A Norman family who came to Ireland in 1170, the Fitzgeralds (spelled Mac Gearailt in parts of Ireland) claimed vast holdings in Cork, Kerry, Kildare, and Limerick. The surname Fitzgerald translates directly as "son of Gerald."
Flynn
The Irish surname Ó Floinn is prevalent in the province of Ulster. However, the "F" is no longer pronounced and the name is now Loinn or Lynn. The Flynn surname can also be found in Clare, Cork, Kerry, and Roscommon.
Gallagher
The Gallagher clan has been in County Donegal since the 4th century and Gallagheris the most common surname in this area.
Healy
The Healy surname is most commonly found in Cork and Sligo.
Hughes
The Hughes surname, both Welsh and Irish in origin, is most numerous in three provinces Connacht, Leinster, and Ulster.
Johnston
Johnston is the most common name in the Irish province of Ulster.
Kelly
Kelly families of Irish origin come primarily from Derry, Galway, Kildare, Leitrim, Leix, Meath, Offaly, Roscommon, and Wicklow.
Kennedy
The Kennedy surname, both Irish and Scottish in origin, hails from Clare, Kilkenny, Tipperary, and Wexford.
Lynch
The Lynch families (Ó Loingsigh in Irish) were originally settled in Clare, Donegal, Limerick, Sligo, and Westmeath, where the Lynch surname is most common.
MacCarthy
The MacCarthy surname originated primarily from Cork, Kerry, and Tipperary. Also spelled McCarthy.
Maguire
The Maguire surname is the most common in Fermanagh. Also spelled McGuire.
Mahony
Munster was the territory of the Mahoney clan, with Mahonys (or Mahoneys) being most numerous in Cork.
Martin
The Martin surname, common in both England and Ireland, can be found primarily in Galway, Tyrone, and Westmeath.
Moore
The ancient Irish Moores settled in Kildare, while most Moores are from Antrim and Dublin.
Murphy
The most common of all Irish names, the Murphy surname can be found in all four provinces. Murphys are primarily from Antrim, Armagh, Carlow, Cork, Kerry, Roscommon, Sligo, Tyrone, and Wexford, however.
Murray
The Murray surname is especially prolific in Donegal.
Nolan
Nolan families have always been very numerous in Carlow, and can also be found in Fermanagh, Longford, Mayo, and Roscommon.
O'Brien
One of Ireland's leading aristocratic families, the O Briens are primarily from Clare, Limerick, Tipperary, and Waterford.
O'Donnell
The O Donnell clans originally settled in Clare and Galway, but today they are most numerous in County Donegal. Sometimes modified to O'Donnelly.
O'Neill
One of three royal Irish families, the O Neills are from Antrim, Armagh, Carlow, Clare, Cork, Down, Tipperary, Tyrone, and Waterford.
Quinn
From Ceann, the Irish word for head, the name Ó Cuinn means intelligent. In general, Catholics spell the name with two ns, while Protestants spell it with one. The Quinns are primarily from Antrim, Clare, Longford, and Tyrone, where their surname is the most common.
Reilly
Descendants of the O Conor kings of Connacht, the Reillys are primarily from Cavan, Cork, Longford, and Meath.
Ryan
The Ó Riain and Ryan families of Ireland are primarily from Carlow and Tipperary, where Ryan is the most common surname. They can also be found in Limerick.
Shea
Originally the Shea family was from Kerry, though they later branched out to Tipperary during the 12th century and Kilkenny by the 15th century. Sometimes modified to Shay.
Smith
The Smiths, both English and Irish, are primarily from Antrim, Cavan, Donegal, Leitrim, and Sligo. Smith is actually the most common surname in Antrim.
Sullivan
Originally settled in County Tipperary, the Sullivan family spread into Kerry and Cork, where they are now most numerous and their surname is the most common.
Sweeney
Sweeney families are found primarily in Cork, Donegal, and Kerry.
Thompson
This English name is the second most common non-Irish name found in Ireland, especially in Ulster. The Thomson surname, without the "p," is Scottish. Thomson is most common in Down.
Walsh
The name came into use to describe the Welsh people who came to Ireland during the Anglo-Norman invasions. Walsh families were very numerous throughout all four provinces of Ireland. Walsh is the most common surname in Mayo.
White
Spelled de Faoite or Mac Faoitigh in Ireland, this common name stems mainly from the "le Whytes" who came to Ireland with the Anglo-Normans. White families can be found in Ireland throughout Down, Limerick, Sligo, and Wexford.
