Clonalis House (Irish: Teach Chluain Mhalais), Castlerea, County Roscommon is the ancestral home of the O'Conor Don, who is a direct descendant of the last High King of Ireland, Ruaidrí Ua Conchobair.
Clonalis was constructed in 1878 by Charles Owen O'Conor as a replacement for an earlier house on the same site which was frequently damaged by flooding. Built of mass concrete, its design by the renowned Pepys Cockerell is of a mixture of styles drawing on the traditions of Italianate and Queen Anne Style architecture.
Some 100,000 volumes are contained in the family archives and library of the O'Conor Don which are still held at Clonalis House, making it a valuable repository of Irish history.
- O'Connor, Roderic, A Historical and Genealogical Memoir of the O'Connors, Kings of Connaught, and their Descendants. Dublin: McGlashan & Gill. 1861.
- O'Donovan, John and the Rt. Hon. Charles Owen O'Conor Don, The O'Conors of Connaught: An Historical Memoir. Dublin: Hodges, Figgis, and Co. 1891.