The Mac Mahon family is of Irish origin. They were Lords of Corcu Baiscind in Ireland and descended from Mahon, the son of Muirchertach Ua Briain, High King of Ireland. After losing much of their land in the Cromwellian confiscations, a branch moved to Limerick for a time before settling in France during the reign of King William III because of their support of the deposed King James II in the Glorious Revolution They applied for French citizenship in 1749; after the definitive installation of the family in France, their nobility was recognised by the patent letter of King Louis XV of France.