Fermoy (Irish: Mainistir Fhear Maí; formerly also Armoy) is a barony in County Cork in Ireland. It is bordered by the baronies of Orrery and Kilmore to the north-west; Duhallow to the west; Barretts to the south-west; Barrymore to the south; Condons and Clangibbon to the east; and Coshlea, County Limerick to the north. It is bounded to the south by the Nagle Mountains and the valley of the Munster Blackwater. The Ballyhoura Mountains mark the northern boundary. A tributary of the Blacckwater, the Awbeg has two branches in its upper stretches; one branch forms the northern boundary while the other near Buttevant, forms the western limit. To the east, lies another Blackwater tributary, the Funcheon. Anomalously, the namesake town of Fermoy is actually in the barony of Condons and Clangibbon. The town with the greatest population in the barony is Mallow (8578 people per Census of 2006).
Baronies were created after the Norman invasion of Ireland as divisions of counties and were used in the administration of justice and the raising of revenue. While baronies continue to be officially defined units, they have been administratively obsolete since 1898. However, they continue to be used in land registration and in specification, such as in planning permissions. In many cases, a barony corresponds to an earlier Gaelic túath which had submitted to the Crown.