McMahon or MacMahon (older
Irish orthography:
Mac Mathghamha reformed Irish orthography: Mac Mathúna) is an
Irish surname. The surname arose separately in two areas: in west Co. Clare and in Co. Monaghan. The Co. Monaghan (
Airgíalla) MacMahons are not related to the Co. Clare (
Thomond) MacMahons.