O'Connor, John (1849–1908), nationalist revolutionary, was born 26 May 1849 in the Glen of Imaal, Co. Wicklow, youngest son of Patrick O'Connor, farmer, and his wife (née Kearney). Educated at a national school, by the age of 16 he was already of a tall and athletic build and, despite his youth, was allowed to join the IRB, of which his older brothers, James O'Connor (qv) and Patrick, were already members. By September 1865 he was the chief messenger between James Stephens (qv), the IRB leader, and T. J. Kelly (qv), his deputy. On the night of Stephens's rescue from Richmond prison (24 November 1865) O'Connor piloted him to safety, hiding him with the family of his sister, a Mrs Boland. He continued to be Stephens's messenger until the latter's escape to America in February 1866. Shortly thereafter, following the suspension of habeas corpus, O'Connor was arrested and held as a suspect in Mountjoy jail for approximately a year. On his release he helped reorganise the IRB under the ‘supreme council’ by firmly establishing its authority in Ulster until the arrest of some Ulster IRB leaders in summer 1867 prompted him to flee the country.
Settling in New York, over the next few years he worked at various odd jobs to earn a living while studying medicine at night. He joined the Napper Tandy Club, the parent branch of Clan na Gael (established 20 June 1867), and, as president of the club (1872–5), was responsible for establishing regular communications between the Clan and IRB. He also assisted John Devoy (qv) in organising the Catalpa rescue in 1875. Shortly after the IRB recognised the Clan as its official ally (August 1876), O'Connor returned to Ireland to reorganise the movement, ultimately being appointed IRB secretary in March 1878. Over the next five years, the IRB's membership rose and peaked at roughly 35,000 men, while O'Connor arranged the purchase of 5,000 firearms which he imported into Ireland from England and Belgium – the most successful such scheme the IRB ever undertook. As he travelled throughout the UK, as well as to France, Belgium, or America, he used various disguises and false names (most frequently ‘Dr Clarke’), as well as secret fraternal links provided by his membership of the freemasons and the IRB, to assist him in evading police supervision.
Following the wishes of C. J. Kickham (qv) and John O'Leary (qv), he toured Connacht during the summer and autumn of 1880, encouraging IRB members to withdraw from a land agitation that was producing only agrarian outrages. During the 1880s he resided mostly in London and Paris, where he worked as a medical assistant and married a German woman, raising one (non-English-speaking) daughter. Like all IRB leaders, he opposed the ‘dynamite war’ which the new ‘Triangle’ leadership of the Clan launched in March 1883. During an American visit in September 1884, O'Connor was threatened with execution by the Triangle if he did not authorise a bogus financial statement to implicate the IRB in the ‘dynamite war’. Thereafter he persuaded John Devoy (qv) to come to his defence, resulting in a long-lasting split in the Clan, which never again truly reunited. Demoralised by the impasse facing the Irish revolutionary movement, in September 1888 O'Connor testified on behalf of the IRB at a Clan ‘trial’ in New York. This resulted in the demise of the Triangle, but the Clan remained divided. In September 1891 he negotiated an alliance between the IRB and the minority wing of the Clan, led by Devoy; but this failed to revive the IRB's fortunes, owing to lack of funding. Dogged by repeated attempts by Irish-American spies to assist British intelligence to track down his movements, O'Connor was forced to retire from the IRB during 1894.
In later years he lived in Paris under the name of Korner, received some employment as a doctor's assistant, but was beset by poverty and a need to maintain complete personal isolation, owing to his past revolutionary career. Believed by British intelligence to have been the IRB's president, in reality he had been its secretary, serving as its chief organiser for approximately fifteen years. Neither his old political associates nor his relatives knew of his exact whereabouts (or that he ever married) until shortly after his death in Paris 21 November 1908. His papers (none of which appear to have survived) were secretly shipped to John Devoy, who described him as ‘neither a speaker nor a writer, he was yet a man of intellect’ (Gaelic American, 5 Dec. 1908). After the disbandment of the IRB, Devoy wrote that John O'Connor was the most efficient secretary it ever had (Gaelic American, 6 Dec. 1924).