50 Most Common Irish Surnames & Their Coats of Arms

Ó (older Ua) means "grandson" or "descendant of"; Mac means "son of"; Ní and Nic are the female forms — a daughter of the Ó Briain is Ní Bhriain. Fitz, from Norman French fils, does the same job for Hiberno-Norman families.

Most prefixes were dropped during the penal era and the eighteenth century and many were restored in the nineteenth and twentieth. So the presence or absence of an O' tells you about the 1800s, not the 1000s.

• Murphy — Ó Murchadha and Mac Murchadha, from murchadh, "sea-warrior". The most common surname in Ireland, and at least two entirely unrelated originals. Wexford, Cork and Armagh.
• Kelly — Ó Ceallaigh, from ceallach. Chiefly of Uí Maine in Galway and Roscommon, but adopted independently in several places.
• O'Sullivan — Ó Súilleabháin, from súil, eye: "one-eyed" or "hawk-eyed". Cork and Kerry, where it is the dominant name.
• Walsh — Breathnach, "the Briton". Not Gaelic in origin at all: it marks the Welsh who came with the Normans after 1169. Scattered across Leinster and Munster.
• Smith — frequently not English. In Cavan and the midlands it is an anglicisation of Mac Gabhann, "son of the smith", translated rather than transliterated.
• O'Brien — Ó Briain, from Brian Bóroimhe, Brian Boru, killed at Clontarf in 1014. Clare, Limerick, Tipperary.
• Byrne — Ó Broin, from bran, raven. Wicklow, where the Byrnes held out against Dublin for centuries.
• Ryan — Ó Riain, and in Tipperary the distinct Ó Maoilriain. Tipperary and Limerick.
• O'Connor — Ó Conchobhair, "lover of hounds". At least six unrelated septs: O'Connor Don of Connacht, O'Connor Kerry, O'Connor Faly of Offaly, O'Connor Sligo and others. A textbook case of one surname, many families.
• O'Neill — Ó Néill, from Niall Glúndub, died 919. Tyrone. The senior Gaelic dynasty of Ulster.
• Reilly — Ó Raghallaigh, lords of East Breifne. Cavan.
• Doyle — Ó Dubhghaill, "dark foreigner": the Irish term for a Dane. The surname records Norse ancestry. Wexford and Wicklow, the old Viking coast.
• McCarthy — Mac Cárthaigh, from cárthach, "loving". Kings of Desmond; Cork and Kerry.
• Gallagher — Ó Gallchobhair, "foreign help". Donegal, where they were the chief military family of the O'Donnells.
• Doherty — Ó Dochartaigh, "obstructive". Inishowen, Donegal.
• Kennedy — Ó Cinnéide, from ceann, head: "helmeted head". Tipperary, and kin to the O'Briens.
• Lynch — two entirely separate names. Ó Loingsigh, from loingseach, mariner; and the Norman de Lench, one of the Tribes of Galway.
• Murray — Ó Muireadhaigh, "lord of the sea", and also the Scottish Moray brought over in the plantations.
• Quinn — Ó Cuinn, from the personal name Conn. Tyrone and Clare.
• Moore — Ó Mórdha, "stately". One of the Seven Septs of Laois. Also, separately, the English Moore.

• McLoughlin — Mac Lochlainn, from a Norse personal name. Donegal and Meath.
• Connolly — Ó Conghaile, "fierce as a hound".
• Daly — Ó Dálaigh. The great hereditary bardic family of Ireland: poets to half the ruling houses.
• O'Connell — Ó Conaill. Kerry.
• Dunne — Ó Duinn, from donn, brown. Laois.
• Brennan — Ó Braonáin. Kilkenny, and separately in Westmeath and Roscommon.
• Burke — de Búrca, from de Burgh: the great Norman house that became Mac William Íochtar and Uachtar. Galway and Mayo.
• Collins — Ó Coileáin, "young warrior". Limerick, later Cork.
• Clarke — Ó Cléirigh, "clerk". The Ó Cléirigh of Donegal produced Mícheál Ó Cléirigh, chief of the Four Masters, who compiled the Annals.
• Hughes — Ó hAodha, from Aodh, fire — one of the commonest Irish personal names, which is why Hughes appears in many unconnected places.
• Fitzgerald — Norman, "son of Gerald", from Gerald of Windsor. Two great branches, Kildare and Desmond, and the shield Argent, a saltire Gules.
• Maguire — Mag Uidhir, "son of the dun-coloured one". Fermanagh, which they ruled outright.
• Nolan — Ó Nualláin, "noble". Carlow.
• Flynn — Ó Floinn, from flann, red. Several unrelated septs.
• O'Donnell — Ó Domhnaill, "world-mighty". Tyrconnell, Donegal. The rivals of the O'Neills.
• Duffy — Ó Dubhthaigh, from dubh, black. Monaghan and Donegal.
• O'Mahony — Ó Mathghamhna, from mathghamhain, bear. West Cork.
• Boyle — Ó Baoighill. Donegal. Not to be confused with the English Boyle of Cork, Earls of Cork.
• O'Shea — Ó Séaghdha, "stately". Kerry.
• Sweeney — Mac Suibhne. A gallowglass family: Hebridean Scots mercenaries settled in Donegal by the O'Donnells in the fourteenth century.

• Kavanagh — Caomhánach, from Domhnall Caomhánach, fostered at the church of St Caomhán. One of the very few Irish surnames that takes neither Ó nor Mac.
• Power — le Poer, Norman, from Old French povre. Waterford.
• Hogan — Ó hÓgáin, from óg, young. Tipperary and Clare.
• Keane — Ó Catháin, from cath, battle. Derry, where they were lords of Keenaght, and Clare.
• Donnelly — Ó Donnghaile, "brown valour". Tyrone.
• Cullen — Ó Cuilinn, from cuileann, holly.
• Sheehan — Ó Síodhacháin, from síodhach, peaceful.
• Hayes — Ó hAodha again, anglicised differently in a different county. The same original as Hughes.
• Gorman — Ó Gormáin, from gorm, blue.
• Larkin — Ó Lorcáin, from lorcc, fierce.

Several of the commonest surnames in Ireland are not Irish at all. Wilson, Johnston, Campbell, Thompson, Brown, Martin, White, Bell, Stewart, Graham, Robinson and Scott arrived overwhelmingly with the Ulster Plantation from 1609 and the Scottish migration that followed it. They are concentrated in Antrim, Down, Armagh, Tyrone and Derry, and their records are Presbyterian rather than Catholic — a different set of registers entirely.

Here is where honesty is required, because this subject is heavily marketed.

Arms in the Irish tradition, as everywhere in Europe, were borne by particular families in particular places, not by everyone sharing a surname. For a name like Murphy or Kelly, an armorial will list several distinct coats, because several distinct and unrelated families bore the name. That is the correct answer, not a limitation of the record.

The way to check it is Burke's General Armory, which is out of copyright, free, and lists Irish arms by surname with the family and place attached. Our guide to verifying a coat of arms sets out how to use it and what the red flags are.

For the Irish heraldic system itself — the Ulster King of Arms, the Chief Herald, the Red Hand, and what the 1922 fire did and did not destroy — see our guide to Irish heraldry.

For any of these names the useful move is the same: find the county and parish, then work the records. Griffith's Valuation (1847–64) and the Tithe Applotment Books are free and cover the period the lost censuses do not; the 1901 and 1911 censuses are free at the National Archives; and the Catholic parish registers are free at the National Library.

The Heritage Volume sets out what the historical record holds for a surname — where it comes from, what it meant, where its bearers were concentrated, and the arms associated with it. How Your Report Is Made explains which parts come from public records and which our system builds.

Display the arms in a framed coat of arms, or carry the crest on a signet ring.