Innisfallen Castle and grounds, Gothic mansion in Castle Cove, Australia

Innisfallen Castle is a sandstone mansion with nine main rooms spread across multiple levels, including a reception room, drawing room, dining room, and four bedrooms. The building sits on a headland overlooking Sugarloaf Bay and Middle Harbour.

Henry Hastings Willis, a former Speaker of the New South Wales Parliament, built the mansion as a family home; work ran from 1903 to 1905 on a site of 55 acres. The first approach was by rowing boat and a rough bush track, and a wharf was added later. The property joined the New South Wales State Heritage Register on 2 April 1999.

Henry Hastings Willis named the house after the ruined abbey at Killarney in Ireland, a reference to his family's Irish origins rather than to any monastic use of the site. The building itself is a late English Gothic design in local sandstone, so the Irish link survives mainly in the name and in the Gothic form chosen for a private family home.

The mansion is privately owned and not open to visitors; it can only be seen from the public road, Cherry Place. The original approach was by rowing boat and a rough bush track, with a wharf added later. Do not enter the grounds, which are private.

The house was named after the ruined Innisfallen Abbey at Killarney, Ireland. Originally the grounds covered 55 acres, and the first access was by rowing boat and a rough bush track before a wharf was added. The property remains privately owned and cannot be entered.