born Oct. 17, 1803, Dromoland, County Clare, Ire.
died June 18, 1864, Bangor, Caernarvonshire, Wales
Irish political insurgent.
He served in the British House of Commons (1828–48) and initially supported the Anglo-Irish legislative union (see Act of Union ). In 1843 he joined the anti-union Repeal Association, and in 1846 he broke with Daniel O'Connell to lead the radical Young Ireland movement. In 1848 he supported violent revolution and led an abortive insurrection in County Tipperary. Convicted of high treason, he received a death sentence that was commuted to exile in Tasmania. He was released in 1854 and pardoned in 1856.
William Smith O'Brien, lithograph by H. O'Neill after a daguerreotype by Glukman, 1848
By courtesy of the trustees of the British Museum; photograph, J.R. Freeman & Co. Ltd.