Doonmore Castle is situated near the village of Doonbeg and beside the Doonmore Cemetery and the lake Doonbeg Lough. The castle is on the shore and is built beside the pier.
The castle was built by Philip Mac Sheeda Nor McCon. The Annals of the Four Masters refer to it as Dun More Mhic an Fhearnachaigh. At the end of the 16th century, the castle was in the possession of Donough Mac Dermot Mac an Fhearmachaigh, but Mahon MacGorman held title to one third of the castle and all of Donough’s land. Sir Daniel O’Brien of Dough owned the castle in 1574. Two decades later, in 1594, Mahon MacGorman assigned his interest in the place to the Earl of Thomond. Murrough MacGucarrick claimed the castle in 1619. Doonmore was confiscated by the crown in 1688 and was sold in 1703.
The castle was still inhabited in 1808, but it was in ruins in 1837. A turret at the south-west corner fell around 1898, bringing most of the walls of the upper room with it. The rest of the castle was pulled down soon after, leaving only the lower portion, from the stone vault down, intact.