More than thirty million Americans claim Irish ancestry — several times the population of Ireland itself — and their surnames are woven through every corner of American life, from Main Street storefronts to the White House. Some names crossed the Atlantic in such numbers that they are now more common in America than at home. Here are the Irish surnames you meet most often in the United States, and what each one originally meant.
Quick Answer: What Are the Most Common Irish Surnames in America?
The Irish surnames most often found in the United States include Murphy, Kelly, Sullivan, Walsh, Ryan, O'Brien, McCarthy, O'Connor, Kennedy, Gallagher, Doyle and Flynn. Most arrived in the great waves of Irish emigration — above all during and after the Famine of the 1840s — and many lost their O' or Mac prefixes along the way. Murphy, Kelly and Sullivan are generally counted the "big three" of Irish America.
Why Are Irish Names So Common in America?
Emigration on a staggering scale. Across the nineteenth century, and especially in the Famine years of the late 1840s, millions of Irish men and women left for America, settling first in cities like New York, Boston, Philadelphia and Chicago and then spreading through the whole country. They arrived with the oldest hereditary surnames in Europe — and often had the O' quietly trimmed off along the way, a story we tell in Why Do Irish Surnames Start With O'? Their descendants now make Irish surnames among the most numerous in the United States.
The Big Three: Murphy, Kelly and Sullivan
- Murphy (Ó Murchú, "descendant of the sea warrior") — Ireland's most common surname and Irish America's too; a name from the south-east that became a byword for Irishness itself.
- Kelly (Ó Ceallaigh, often read as "bright-headed" or "strife") — borne by several unrelated Irish families, which helped make it ubiquitous on both sides of the Atlantic.
- Sullivan (Ó Súilleabháin, commonly linked to "dark-eyed") — a great Munster name, overwhelmingly from Cork and Kerry, the counties that sent so many to America.
The Rest of the American Top Tier
- Walsh — "Welshman," the name given to settlers arriving from Wales; one of Ireland's most common names.
- Ryan (Ó Riain) — a Tipperary powerhouse of a name, hugely multiplied in America.
- O'Brien — "descendant of Brian," the royal line of Brian Boru himself.
- McCarthy (Mac Cárthaigh, "loving") — the great kings of Munster, and proof that Ireland uses Mac as freely as Scotland (see Mc vs Mac).
- O'Connor (Ó Conchobhair) — descendants of the kings of Connacht.
- Kennedy (Ó Cinnéide, "helmeted head") — a Dal gCais name of Brian Boru's own kin, carried to the American presidency.
- Gallagher (Ó Gallchobhair, "foreign help") — the great name of Donegal.
- Doyle (Ó Dubhghaill, "dark foreigner") — a name recalling Ireland's Viking encounters.
- Flynn (Ó Floinn, from "ruddy") — found across Ireland and everywhere in America.
How Does This Compare to Scottish Names in America?
Scotland ran its own great emigration to America, and its clan names — the MacDonalds, Campbells, Stewarts and their kin — tell a parallel story, which we count down in The Most Common Scottish Clan Names in America. And a fascinating middle ground exists: names that are genuinely both Scottish and Irish, carried between the islands by mercenaries, planters and migrants — the subject of Surnames That Are Both Scottish and Irish.
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Frequently Asked Questions
What is the most common Irish surname in America?
Murphy is generally counted the most common Irish surname in both Ireland and the United States, with Kelly and Sullivan close behind.
How many Americans have Irish ancestry?
More than thirty million Americans claim Irish ancestry — several times the population of Ireland itself.
Why do many Irish-American names lack the O'?
The prefix was widely dropped under anglicisation and during emigration — Sullivan from Ó Súilleabháin, for example — though many families later restored it.
Are Kennedy and McCarthy Irish or Scottish?
Both are Irish Gaelic names — Kennedy from Ó Cinnéide and McCarthy from Mac Cárthaigh — though Kennedy also has a separate Scottish line, making it one of the names found in both traditions.
Find Your Name on the Map
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