Ross Castle (Irish: Caisleán an Rois) is a 15th-century tower house and keep on the edge of Lough Leane, in Killarney National Park, County Kerry, Ireland.

The castle was amongst the last to surrender to Oliver Cromwell's Roundheads during the Irish Confederate Wars,[5] and was only taken when artillery was brought by boat via the River Laune.

Lord Muskerry (MacCarthy) held the castle against Edmund Ludlow who marched to Ross with 4,000 foot-soldiers and 200 horse; however, it was by water that he attacked the stronghold.

At the end of the wars, the Brownes were able to show that their heir was too young to have taken part in the rebellion and they retained the lands.

By about 1688, they had erected a mansion house near the castle, but their adherence to King James II of England after the Glorious Revolution caused them to be exiled.

There is a legend that O'Donoghue leapt or was sucked out of the window of the grand chamber at the top of the castle and disappeared into the waters of the lake along with his horse, his table and his library.

Windows at the lower levels were vertical thin slits preventing entrance into the structure but allowing persons inside to aim and fire arrows or guns at attackers.

The parapet at roof level is 'crenellated' providing ups, 'merlons' and downs, 'crenels', to allow defenders to hide behind the merlons while firing arrows or guns through the crenels.