Molloy or O'Molloy is an Irish surname, anglicised from Ó Maolmhuaidh, maolmhuadh meaning 'Proud Chieftain'.
They were part of the southern Uí Néill, the southern branch of the large tribal grouping claiming descent from Niall of the Nine Hostages, the fifth-century king who supposedly kidnapped St Patrick to Ireland.
They held power over a large part of what is now County Offaly, where the surname is still very common.
A second family were the O Maoil Aodha, 'descendant of the devotee of (St) Aodh', from maol, literally 'bald', a reference to the distinctive tonsure sported by early Irish monks.
The name arose in east Connacht, in the Roscommon/east Galway region, and remains numerous there today.