Ó Meachair or O'Meachair (anglicised as Mahar, Maher, Mahir, Marr, Meagar, Meagher, Meaher, O'Maher and O'Meagher) is a Gaelic Irish surname.
Ó Meachair literally means grandson/descendant of ('O' prefix) the kind, generous or hospitable (Meachair).
By the Irish name convention, this becomes "descendant of a kind, hospitable chief (clan leader)".
The Ó Meachair sept was part of the Ely O'Carroll clan and was concentrated in the areas of Kilkenny and Tipperary, notably the Barony of Ikerrin in Ireland.
According to historian C. Thomas Cairney, the O'Mahers were one of the chiefly families of the Éile tribe who in turn came from the Dumnonii or Laigin who were the third wave of Celts to settle in Ireland during the first century BC.