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Coat of Arms of MacMahon of Clare/Thomond

McMahon or MacMahon (UK: /məkˈmɑːn/,[1] US: /məkˈmæn, -ˈmən, -ˈmɑːn/; older Irish orthography: Mac Mathghamhna reformed Irish orthography: Mac Mathúna) is an Irish surname. The surname arose separately in two areas: in west County Clare and in County Monaghan. The County Monaghan (Airgíalla) MacMahons are not related to the County Clare (Thomond) MacMahons.


The Thomond MacMahons were part of the great tribal grouping, the Dál gCais, and claimed descent from Mahon O'Brien, grandson of Brian Ború. The last chief of the name was killed at the battle of Kinsale in 1602, and the chiefly line became extinct.

After the defeats of the native Irish in 17th century, many of the Clare MacMahons emigrated to serve in the Irish Brigade of the French Army. John Baptiste MacMahon, descended from the MacMahon female line, took on the surname of MacMahon and was the son of one of the original members of the Irish Brigade. He was made Marquis d’Eguilly by Louis XV. He had wanted to marry into a noble family but had to prove he was a noble. The name was changed through the female line because France recognised the line through a female, unlike Ireland to this day.

His grandson, Patrice de MacMahon (1808–1893), was created Duke of Magenta, became a field marshal and later the French president. The MacMahon family are still prominent in France; the family home is the Château de Sully outside Dijon.[2]


Map of Gaelic Ireland circa 900 A.D.

The Oriel (Anglicisation of Airgíalla) MacMahons were based in the barony of Truagh in the north of County Monaghan and ruled the kingdom of Oriel between the thirteenth and the sixteenth centuries. Their last chief, Hugh Oge MacMahon, who had become a lieutenant-colonel in the Spanish army, was beheaded by the English in 1641. A separate McMahon family in County Fermanagh is descended from Mahon Maguire, a grandson of Donn Carrach Maguire. Today, although widespread throughout Ireland, MacMahon remains most common in the two ancestral homelands of Counties Clare and Monaghan.[3]

John O'Hart notes that the MacMahons (sometimes there O'Mahons) were earlier chiefs of the over-kingdom of Ulaid, which then bordered Airgíalla.[4]


  • Niall McMahon (Ladrannaibh, or the bandit), (early 12th century)
  • Ross Bui McMahon (late 16th century)
  • Brian Mac Hugh Og of the Dartrey MacMahons (late 16th century)
  • Raymond McMahon of the Killyleen Mc Mahons (late 17th century)
  • Nicholas McMahon of the Cluaincoinin Mc Mahons (early 19th century)
  • Patrick McMahon of the Cluaincoinin Mc Mahons (late 19th century)
  • Martin McMahon [Motto] of the Cluaincoinin Mc Mahons (early 20th century)
  • John McMahon [Jack Martin]of the Cluaincoinin Mc Mahons (late 20th century)


The motto of the Thomond sept of McMahons is "Sic Nos Sic Sacra Tuemur", which means "Thus We Defend Our Sacred Rights".


"McMahon" is the family name of the following people:




  • Brian MacMahon (1923-2007), British and American epidemiologist
  • James McMahon, contemporary American amateur astronomer
  • Lee E. McMahon (1931-1989), American computer scientist known for his work on the early Unix operating system and on the McMahon system tournament
  • Percy Alexander MacMahon (1854–1929), British soldier and mathematician
  • Thomas A. McMahon (1943-1999), American professor of applied mechanics and biology at Harvard, accredited novelist



The McMahon wrestling family of WWE fame:

  • Jess McMahon (1882–1954), boxing and wrestling promoter; father of Vince McMahon Sr., grandfather of current chairman Vince McMahon, founder of Capitol Wrestling Corporation
  • Vince McMahon Sr. (1914–1984), wrestling promoter and founder of WWE's immediate predecessor company, the World Wide Wrestling Federation
  • Vince McMahon (born 1945), chairman of the board, CEO and majority shareholder of World Wrestling Entertainment, Inc. (dba WWE, Inc.)
  • Linda McMahon (born 1948), wife of Vince Jr., former CEO of WWE and current Administrator of the Small Business Administration.
  • Shane McMahon (born 1970), son of Vince Jr. and former Executive President of WWE Global Media
  • Stephanie McMahon Levesque (born 1976), daughter of Vince Jr. and Chief Brand Officer of WWE

Ships of the surname[edit]

MV Empire MacMahon was an oil tanker converted by the British for WWII service as a merchant aircraft carrier or MAC ship, that is an escort carrier for anti-submarine warfare, an anti-submarine warfare carrier.

See also[edit]


  1. ^ Jones, Daniel; Roach, Peter, James Hartman and Jane Setter, eds. Cambridge English Pronouncing Dictionary. 17th edition. Cambridge UP, 2006.
  2. ^
  3. ^
  4. ^ John O'Hart, Irish Pedigrees; or, The Origin and Stem of the Irish Nation, 5th edition, in two volumes, originally published in Dublin in 1892, reprinted, Baltimore: Genealogical Publishing Company, 1976, Vol. 1, p 819