O'Brien, James Francis Xavier (1828–1905), nationalist, was born 16 October 1828 in Dungarvan, Co. Waterford, second son of Timothy O'Brien (d. 1854), a prosperous merchant; nothing is known of his mother. After attending a local private school, he studied for one term as a divinity student in St John's College, Waterford, but abandoned his studies upon becoming caught up in the wave of republican enthusiasm in Ireland during 1848. Following the initiative of J. F. Lalor (qv), he organised a new, revolutionary secret society in Dungarvan in the summer of 1849, but once a warrant was issued for his arrest he fled to south Wales in one of his father's cargo ships, hiding there for several months. When he returned to Ireland, he spent a few years working for family businesses in Fermoy, Lismore, and Clonmel before enrolling as a medical student at QCG sometime during 1854. Here he renewed his friendship with John O'Leary (qv), who persuaded him to move to Paris, where he studied medicine at L'École de Médecine and served in three different hospitals. Returning to Ireland in the summer of 1856 due to ill health, he was advised by the eminent physician Sir Dominic Corrigan (qv) to take a holiday. He set sail for New Orleans, Louisiana, but on arrival was persuaded by Joseph Brenan (qv) to join a desperate, filibustering expedition by sea to conquer Nicaragua. During mid voyage (April 1857) the expedition was halted by the US navy and its members arrested. After quarrelling with other members of the crew in prison, he feared assassination and so, with great reluctance, asked for the protection of the British consul in New Orleans. Shortly after his release, he spent four months as a lecturer in the Jesuit College in Baton Rouge, Louisiana, replacing Richard D'Alton Williams (qv), before setting up a wholesale business in New Orleans.
Following the outbreak of the American civil war (April 1861), he enlisted as an assistant surgeon with a confederate militia regiment, but as this caused his business to go into bankruptcy, in November 1862 he decided to leave the army and return to Ireland, settling at 6 North Abbey Square in Cork city. Here he became the assistant manager of a tea- and wine-merchant firm. By 1864, due to his past association with O'Leary as well as the Fenian Brotherhood in America, he had become a frequent contributor to the Irish People. His columns (published under the pen name ‘De L'Abbaye’) were generally considered the most anti-clerical in the paper, although he was, in reality, a devout catholic and no longer so very keen a rebel. After the suppression of the Irish People and arrest of the IRB leadership (September 1865), he went into hiding. In February 1867, during a meeting of the Cork IRB, he rejected the plan of Thomas J. Kelly (qv) for a rising because the organisation had virtually no weapons. When he was outvoted on the question, however, he felt compelled to take part, and on 6 March 1867 he led the unarmed IRB force that captured the police barracks in Ballyknockane, Co. Cork. Within hours, however, his men were forced to disperse by the approach of a body of infantry, and he was arrested the following day near Kilmallock, Co. Limerick. On 27 May he was tried for high treason in Cork and sentenced to be hanged, drawn, and quartered, the last Irish felon to receive that particular sentence; but it was soon commuted to penal servitude for life. He was imprisoned in Mountjoy gaol and subsequently in Millbank and Portland gaols in London, where he suffered a long term of solitary confinement. However, thanks to the amnesty movement, along with C. J. Kickham (qv), he was released on 4 March 1869 and, returning to Cork, began working as a commercial traveller for his former employers.
Shortly after his release from prison, he was elected a member of the IRB supreme council, and in this capacity helped to draft its first constitution (adopted 18 August 1869) and supported the nomination of Jeremiah O'Donovan Rossa (qv) for parliament in order to embarrass the government; a ploy that succeeded when Rossa was elected (25 November 1869; declared ineligible 10 February 1870). Although John Devoy (qv) later heard rumours that O'Brien was the IRB president at this time, O'Brien's own recollections indicate that he was only the supreme council representative for Munster and a very apathetic one at that, for he felt ill-equipped to organise such a movement. By 1871 he was fully determined to leave the IRB, but due to pressure from his associates he could not formally do so until December 1874. Settling at Rose Cottage, Blackpool Road, Cork, for the remainder of the decade he worked as the secretary of the Cork Gas Co., founded by Denny Lane (qv), and retired from all political activity, though he remained a very close friend of Kickham.
In 1882, together with W. H. O'Sullivan (qv), he established a tea- and wine-merchant business in Dublin which later extended its operations to London. In November 1885, after C. S. Parnell (qv) failed to persuade the Mayo National League to withdraw the IRB prisoner P. W. Nally (qv) as their nominee for parliament, the Irish party leader approached O'Brien and persuaded him to reenter politics. Trading on his reputation as an 1867 rebel and promising to demand Nally's release, O'Brien was accepted as the parliamentary candidate and stood successfully for Mayo South, although once elected it seems he never raised Nally's case. As an MP, O'Brien took little or no part in Westminster affairs except to vote with the Irish party when requested, but he played a very important administrative role in organising the party. On moving to London (1888) he became treasurer of the Irish National League of Great Britain and two years later was appointed general treasurer of the Irish National League in Ireland as well, thereby effectively giving him the responsibility of financing all Irish party electoral campaigns. Soon after the split in the party (December 1890), he became general treasurer of the anti-Parnellite Irish National Federation. In this capacity, however, he was politically embarrassed in August 1894 when it was revealed that he had been persuaded by John Dillon (qv) to issue a circular appealing to the liberal party to finance Irish party MPs' election campaigns. With the support of the Healy family, he was elected to parliament for Cork city (1895), a position he held until his death ten years later, but ill health generally prevented him from attending the house of commons and he continued to perform a purely administrative role. Appointed general secretary of the United Irish League in 1900, he announced his intention to retire in early 1905, but while preparing to hand over his duties he contracted pleurisy and died of heart failure on 28 May at his residence, 39 Gauden Road, Clapham, London. In accordance with his wishes he was buried in Glasnevin cemetery. He married first Mary Louise Cullimore (d. August 1866); they had one son, who later became a catholic priest in Dublin. He married secondly (1870) Mary Teresa O'Malley, with whom he had three daughters and two sons. His papers, which include the financial records of the Irish party and an unfinished autobiography (MS 16695), are kept in the NLI.