Nestor is, apart from a given name, also found as a surname borne by Irish and Estonians.
In Ireland, it was derived as a shortened form of Mac Girr an Adhastair, meaning son of the short man of the bridle. It was sometimes shortened to Mac an Adhastair. The surname is most common in County Galway and County Clare. The clan were natives of Corcomroe in the latter county, which in the Middle Ages formed the north-westernmost territory of the kingdom of Thomond. The Mac Girr an Adhastair were associated with the local lords, the Ó Lochlainn family.
Notable people with the surname include: