Hamilton, William Henry (c.1771–1825), United Irishman, soldier, and journalist, was the son of Johnston Hamilton, attorney, of Enniskillen, Co. Fermanagh. He received a good education and at a young age showed ability as an actor and writer. His talents attracted the attention of the earl of Enniskillen, who in September 1793 helped him secure a commission as ensign in Capt. Dunne's independent infantry company. Prominent in radical politics in Co. Fermanagh, he and Thomas Russell (qv) founded a Society of United Irishmen in Enniskillen in October 1793. His politics soon alienated the earl, and Hamilton sold his commission in January 1794. On 29 January 1794 he married Russell's niece, Mary Ann Russell (c.1775–c.1840), who herself had radical political views; she was the elder daughter of Thomas Russell's eldest brother John (qv). He then went to London to study law at the Inns of Court and was called to the English bar. A member of the radical London Corresponding Society and of the United Britons committee which sought to coordinate the activities of English and Irish republicans, he fled to France in the spring of 1798 after the arrest of Arthur O'Connor (qv) and other United men. On 6 September 1798 he sailed on board the Loire in Gen. Jean Hardy's expedition to Ireland (Theobald Wolfe Tone (qv) was a member of the same expedition). The French fleet was intercepted and defeated by the Royal Navy off Lough Swilly on 12 October. Taken prisoner, Hamilton was suspected of being an Irishman because of his height, but his fluent French and the fact that he wore an earring allayed his captors’ suspicions and he was exchanged as a French prisoner of war.
In France he was active among United Irish émigrés, and late in 1802 he joined Robert Emmet (qv) who was planning an insurrection in Ireland. Hamilton was one of Emmet's main organisers and returned to Ireland via London in January 1803 to test the waters for insurrection and raise funds. The response he met with was sufficiently generous, and the state of the country sufficiently disturbed, to convince him that another rising stood a real chance of success, even without the intervention of French troops. On his return to Paris in February he reported his findings to his United Irish colleagues and began to recruit exiled Irishmen to take part. He then travelled to Brussels, where he persuaded T. A. Emmet (qv) and W. J. MacNeven (qv) to go to Paris to act as United Irish ambassadors. On 5 March he returned to Ireland and prepared for the rising, staying at Robert Emmet's headquarters in Butterfield Lane, Rathfarnham, Co. Dublin. He was assigned to help Thomas Russell raise Ulster, and went there towards the end of June 1803. He tried to raise Co. Cavan and Co. Fermanagh but received no support, after which Russell summoned him to Co. Antrim. Around 22–4 July he attempted to call out United Irish sympathisers in Belfast, Ballymena, and Templepatrick, but they too failed to respond.
He then went into hiding, making his way to Ballybay, Co. Monaghan. A notice offering £300 for his apprehension described him as ‘about six feet high, slender make, fair complexion, strong beard, large dark blue eyes, his nose a little turned up, a small dimple in his chin, dark brown hair, genteel address and swaggering walk’ (Madden, 217–18n). In October 1803 he was arrested while sleeping in a hut by Lough Egish, and imprisoned in Kilmainham jail until the restoration of habeas corpus on 8 March 1806. The under-secretary at Dublin Castle, Alexander Marsden (qv), described Hamilton as ‘a clever fellow, perhaps the most so of any engaged in Emmet's schemes’ (16 May 1804, NA (Kew), HO 100/122/220). After his release he was employed for several years on Dublin newspapers, becoming a regular contributor to the Dublin Evening Post and later joint editor (c.1817–21). He wrote a play, ‘The portrait of Cervantes’, which was staged at Crow St. theatre, Dublin, and he may also have written the libretto to the opera ‘The magician without magic’, first performed in Dublin in 1815.
As editor of the Evening Post, from 1817 he promoted Bolívar's campaign to liberate Spanish America. Despite being aged near 50, he went to South America to assist Bolívar in about March 1821, and was appointed colonel in the Colombian army. Sent on missions to the USA, in June 1823 he was in Philadelphia negotiating the purchase of a ship. While on his way to Bogotá, possibly returning from the USA, he died of fever at Santa Anna on the River Magdalena in Colombia on 26 December 1825, and was buried in a sandbank. An obituary noted that he died ‘distinguished by the respect of the most exalted characters’ in the United States and Colombia (Enniskillen Chronicle and Erne Packet, 20 Apr. 1826).
He and his wife had at least two children, including a son who survived him.