The Healy surname can most commonly be found in Cork and Sligo.
The Hughe surname, both Welsh and Irish in origin, is most numerous in 3 provinces: Connacht, Leinster, and Ulster.
Johnston is the most common name in the province of Ulster.
Kelly families of Irish origin come primarily from Derry, Galway, Kildare, Leitrim, Leix, Meath, Offaly, Roscommon, and Wicklow.
The Kennedy surname, both Irish and Scottish in origin, hails from Clare, Kilkenny, Tipperary, and Wexford.
The Lynch families (Ó Loingsigh in Irish) were originally settled in Clare, Donegal, Limerick, Sligo, and Westmeath, where the Lynch surname is most common.
The MacCarthy surname originated primarily from Cork, Kerry, and Tipperary.
The Maguire surname is the most common in Fermanagh.
Munster was the territory of the Mahoney clan, with Mahonys being most numerous in Cork.
The Martin surname, common in both England and Ireland, can be found primarily in Galway, Tyrone, and Westmeath.
The ancient Irish Moores settled in Kildare, while most Moores are from Antrim and Dublin.
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.
The Murray surname is especially prolific in Donegal.
Nolan families have always been very numerous in Carlow, and can also be found in Fermanagh, Longford, Mayo, and Roscommon.
One of Ireland's leading aristocratic families, the O Briens are primarily from Clare, Limerick, Tipperary, and Waterford.
The O Donnell clans originally settled in Clare and Galway, but today they are most numerous in Donegal.
One of three royal Irish familes, the O Neills are from Antrim, Armagh, Carlow, Clare, Cork, Down, Tipperary, Tyrone, and Waterford.
From Ceann, the Irish word for head, the name, Ó Cuinn, means intelligent. In general, Catholics spell the name with two "n"s while Protestants spell it with one. The Quinns are primarily from Antrim, Clare, Longford and Tyrone, where their surname is the most common.
Descendants of the O Conor kings of Connacht, the Reillys are primarily from Cavan, Cork, Longford, and Meath.
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.
Originally the Shea family was from Kerry, though they later branched out to Tipperary during the 12th century and Kilkenny by the 15th century.
The Smiths, both English and Irish, are primarily from Antrim, Cavan, Donegal, Leitrim, and Sligo. Smith is actually the most common surname in Antrim.
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 families are found primarily in Cork, Donegal and Kerry.
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 and is the most common in Down.
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.
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 fnd in Ireland throughout Down, Limerick, Sligo, and Wexford.