O’Donnell is born in an army barracks in Devon, England, where his father, Sergeant Bernard MacDonald, is stationed. His mother, Mary Kain, is a native of Ballybane, close to Galway city. He is educated at the Erasmus Smith School in Galway, Coláiste Iognáid (the “Jes”), and later enrolls in Queen’s College Galway, where he studies English literature, history and political economy. While a student at the college, he acquires a considerable reputation as an orator, and is a frequent contributor to meetings of the college’s Literary and Debating Society, of which he becomes vice-auditor for the 1864–65 session.
Even in his student days, O’Donnell seems to be quick to voice his opinions, and revells in controversy. In November 1866, addressing the Literary and Debating Society on the question “Was the character of Warren Hastings as Governor-General of India praiseworthy?,” he causes uproar by denouncing “the principle and the system which have lain at the root of the international and intercolonial policy of England, from the days when Elizabeth, the Infamous, chartered for profit two of the first ships which opened the African slave trade.” His remarks cause the chairman of the meeting, Professor Thomas Moffett, to prevent him from continuing his speech, stating that “such an epithet ought not to be applied to any predecessor of our present gracious Queen.” O’Donnell regards such action as an unwarranted restriction on his freedom of speech, and in a letter published in the local press gives an early example of his high-flown literary style:
“I hold that Debating Societies are the nurseries of independent thought, and the training schools of sober criticism. I believe in the power and impartiality of an enlightened studenthood … I have followed the mind of Austin. I have sat at the feet of Cairnes. I have drunk of the philosophy of Mill. I claim for Judicial Science, for Economic Science, for the Philosophy of History, a place in the discussions of our society, I pity and I scorn the formidable confederacy of fools who dare not call a spade a spade.”
This incident, combined with the reluctance of the society to prevent O’Donnell from addressing its meetings, eventually leads to the suspension of the society from the Queen’s College and its temporary migration to rooms in the city of Galway.
O’Donnell graduates from the Queen’s College with an M.A. degree in 1868, winning several gold medals for his academic performance. By this stage, he has begun to style himself ‘Frank Hugh O’Donnell,’ believing himself to be a descendant of Hugh O’Donnell, 2nd Earl of Tyrconnell.
Leaving Galway, O’Donnell moves to London, where he embarks on a career in journalism, following his college contemporary T. P. O’Connor. O’Connor’s knowledge of modern European languages has helped him to establish himself as a correspondent on European affairs, and he assists O’Donnell in developing a similar reputation. He spends a brief period on the staff of The Morning Post.
In the 1874 United Kingdom general election, O’Donnell is elected Member of Parliament (MP) for Galway Borough, but is unseated by the courts in what appears to be a politically inspired judgment which uses certain unsavoury campaigning tactics in which O’Donnell had indulged as its basis. He is succeeded in the seat by his election agent, Dr. Michael Francis Ward, who is himself succeeded in 1880 by T. P. O’Connor in an unusual succession, all three having been either auditor or vice-auditor of the Queen’s College Literary and Debating Society in the same era.
In 1875, O’Donnell is a founding member of the Constitutional Society of India, a group promoting political autonomy for India. In 1877, he secures a more permanent election to the House of Commons of the United Kingdom as MP for Dungarvan. He holds the seat until 1885, when the constituency is abolished. He strikes a colourful and controversial figure in parliament and becomes renowned for his declamatory speech-making. He is a prominent obstructionist and claims credit for inventing the tactic of obstructionism which is to yield such results for the Home Rule League under Charles Stewart Parnell. Indeed, he sees himself as a natural leader and becomes disillusioned when Parnell is selected in May 1880 to succeed William Shaw as leader of the Irish Parliamentary Party. He calls the British ‘Imperial pirates’ and inaugurates the Constitutional Society of India. Its aim is Home Rule for India, “Mr. O’Donnell’s grand passion in politics was a confederation of all the discontented races of the Empire under the lead of the Irish party. He once brought down some scores of dusky students of all the races and creeds of Hindustan to the House of Commons.”
Parnell refuses to let O’Donnell be nominated in 1885. He leaves the Irish Parliamentary Party and conventional politics, but not its general aims of promoting home rule and tenant farmers’ rights. His last and perhaps most important contribution to the fortunes of the party is the libel case he launches against The Times in 1888 over the series “Parnellism and Crime.” Though the case is lost, it results in the establishment of the Parnell Commission which exonerates Parnell from condoning the Phoenix Park Murders, and exposes the Pigott Forgeries.
In his later years O’Donnell begins investigating misconduct by both the British Civil Service and the Roman Catholic church in Ireland. His Paraguay on Shannon (1908) is an amusing but serious critique of unethical practices by the Catholic clergy in local politics, education, and their involvement in the Congested Districts Board for Ireland that is financed by Parliament in order to improve the depressed economy of western Ireland. Parliament believes that by improving the living standards of the Irish peasant class, they can “kill Home Rule with kindness.”
After careful investigation, O’Donnell accuses members of the Catholic clergy of illegally diverting Government money earmarked for economic development into new Cathedrals, parish churches, and other ecclesiastical building projects. He argues that the British Government needs to provide better oversight of how the Congested Districts Board’s funds are being used. He believes that “in Ireland material ruin has accompanied clerical despotism.” His hostility to the Church draws the ire of Catholic historians who systematically undermine his credibility.
Ernest Belfort Bax writes that O’Donnell’s “matter is better than his manner.”