Rossmore Castle, Gothic castle ruins in County Monaghan, Ireland.

Rossmore Castle was a Gothic-style country house built in 1827 for the 2nd Baron Rossmore to designs by William Vitruvius Morrison. A large square tower with a turret and crow-stepped battlements dominated the building, which also had gables and oriel windows. William Henry Lynn extended and remodelled it in 1858, and repeated enlargements left it with three towers and over 117 windows in at least 53 sizes and shapes.

Rossmore Castle was built in 1827 for Warner Westenra, 2nd Baron Rossmore, to designs by William Vitruvius Morrison in the Gothic style. It was extended and remodelled in 1858 by William Henry Lynn. After the Second World War dry rot forced the family to move to Camla Vale, and the castle was demolished in 1975.

The residence reflected the architectural evolution of Irish country houses through its combination of Tudor Gothic and Scottish Baronial design elements.

The castle itself no longer stands: it was demolished in 1975, and only some ivy-covered wall fragments remain in Rossmore Park. The park is open to visitors, and the grounds passed to An Taisce in 2021. Look for the surviving masonry rather than a building, and allow time to walk the former estate.

The castle contained 117 windows in 53 different shapes and sizes, a result of multiple expansions. This unusual collection came from a competition among residents over who could have the largest room in the county.