Mountshannon House, Neo-Palladian country house in Lisnagry, County Limerick, Ireland

Mountshannon House is a ruined neo-Palladian country house in Lisnagry, County Limerick. Its seven-bay entrance front was framed by four Ionic columns, and a large conservatory stood at the rear. The house was burnt in 1920 and partly demolished; the front columns and most of the main wings still stand.

The house was built in the mid-18th century as the residence of John FitzGibbon, the first Earl of Clare and Lord Chancellor of Ireland. Its construction reflected the wealth and political power of the Anglo-Irish gentry during that period.

John FitzGibbon, created Earl of Clare in 1795, was known nationally as "Black Jack Fitzgibbon" for his opposition to Catholic emancipation, yet the FitzGibbon family was regarded locally as fair landlords. The estate's 900-acre demesne, bounded by the Mulkear River and the Shannon, was worked and maintained by a large household staff.

The house stands in Lisnagry near Castleconnell, County Limerick, on the road from Annacotty to Newgarden. The estate once covered 900 acres (3.6 km2), bounded by the Mulkear River to the south and the Shannon to the west. Much of the boundary wall survives along the modern Mountshannon road, so the ruin can be reached by following that road.

The estate's boundary wall ran about two and a half miles along the Limerick to Castleconnell road, from Annacotty to Newgarden, and many stretches of it survive beside the modern Mountshannon road. The house itself was burnt in 1920 during the Anglo-Irish War; the front Ionic columns and most of the main wings still stand.