Butler, Simon (1757–97), United Irishman and lawyer, was born in July 1757, third son among five children of Edmund Butler (d. 1779), barrister and 10th Viscount Mountgarret, and his wife Charlotte (d. 1778), daughter of the barrister Sir Simon Bradstreet (1693–1762). He entered the Middle Temple (September 1772) and was called to the bar (1778); in 1784 he became a KC and a bencher of the King's Inns, Dublin. He chaired the first meeting of the Dublin Society of United Irishmen 9 November 1791, a distinction he probably owed as much to his lineage as his ability, and chaired most subsequent meetings in the following year. He often acted as legal adviser to the society and the Catholic Committee; on 21 January 1792 he produced a report for the United Irishmen detailing the severity of the remaining restrictions on catholics under the penal laws. This formed the basis for his Digest of the popery laws (1792) which, according to T. A. Emmet (qv), ‘brought the whole of that monstrous code under one view, made reference to its detailed enormities easy, and effected more in bringing the system and its authors into abhorrence, than had ever been done by any other publication’ (MacNeven, 122). It also earned him £500 from the Catholic Committee a year later. He acted as counsel for James Napper Tandy (qv) in June 1792, wrote a number of United Irish addresses, and was one of the deputation sent to the Catholic Convention in December 1792. In February 1793 he was again elected chairman of the United Irishmen and appointed to the society's parliamentary reform committee, which in April 1793 produced radical proposals for annual parliaments and universal male suffrage. In February 1793 he and Oliver Bond (qv), as respective chairman and secretary of the Dublin United Irishmen, published a declaration questioning the authority of a house of lords secret committee on Defender disturbances, and criticised their ‘inquisitorial’ methods. The lords responded by finding them guilty of libelling the high court of parliament, sentenced them to six months' imprisonment, and fined them £500 each, a punishment generally considered excessively severe. Butler was also dismissed as a KC. On 1 March 1793 they were committed to Newgate prison, Dublin. Regarded as martyrs to liberty in radical circles, they enjoyed comfortable prison conditions, hosting several lavish dinners (paid for by United Irish colleagues) as a gesture of defiance to the government. Butler, however, tested the society's generosity by running up enormous bills for fruit (£12) and wine (£100); the last straw for many members was the report that his mistress was seen taking away large baskets of delicacies from the prison. He had easy access to visitors and in May 1793 met the French agent Eleazer Oswald, who had come to Ireland to sound out support for a French invasion. He was released on 16 August 1793, his fine mostly paid by the United Irishmen.
When the sentence had been passed, Lord Chancellor John Fitzgibbon (qv) had strongly reprimanded Butler, claiming that he had disgraced his family and his profession. Butler sought satisfaction in October 1793 but, after Fitzgibbon refused to treat the matter as private and threatened Butler with further legal penalties, he desisted. In early November 1793 Butler and Archibald Hamilton Rowan (qv) attended the radical ‘British convention’ at Edinburgh as representatives of the United Irishmen, and were honoured with a dinner in Belfast on their return journey (13 November 1793). In February 1794 Butler failed to be elected to important United Irish committees after rumours circulated that he was negotiating with the government through his nephew's father-in-law, Robert Fowler (qv), archbishop of Dublin 1779–1801. Butler appears to have grown increasingly disillusioned with radical activity in these months, frequently expressing his contempt for the timidity of the people in general and the catholics in particular. He met the French agent, the Rev. William Jackson (qv), in April 1794, but avoided any entanglement in his scheme by treating his invasion proposals as a joke. After the police dispersed a United Irish meeting on 23 May 1794, Butler called for the society to meet openly and challenge the legality of any future interference. William Drennan (qv) admired his courage and selected him as one of his defence counsel for his trial in June 1794. Oppressed by heavy debts in the mid-1790s, Butler had less involvement with the underground United Irishmen than with the constitutional society. However, in April 1795 an informant listed him as a member of the clandestine Strugglers’ Club, which consisted of leading United Irishmen, and he was also reported as inciting catholics to riot after the dismissal of Viscount Fitzwilliam (qv) in February 1795. Recognising the professional losses he had sustained by supporting catholic relief, in 1795 the Catholic Committee stepped in to prevent the sale of his library. He died 19 May 1797 at his lodgings in Brompton Row, London, and was buried in a vault at St James's church, London.
He married (18 January 1795) Eliza Lynch (d. 1800) of Hampstead, Co. Dublin; they had a son, Edward Lynch Butler (b. 1796), who married a daughter of Henry Sheares (qv); he also had a daughter outside marriage. Simon's elder brother was Edmund Butler (1745–93), 11th Viscount Mountgarret (1779–93), ‘an excellent scholar, a man of strong intellect, of a violent disposition remarkable for his fortitude and courage . . . [and] an excellent parliamentary speaker’ (Gent. Mag. (1793), lxiii, pt 2, 678). For several years he was an ardent Patriot but in his latter years he supported the government. He was succeeded by his eldest son Edmund Butler (1771–1846), 12th Viscount Mountgarret (1793–1846), who was created earl of Kilkenny 2 December 1793; he married (8 June 1793) Mildred, daughter of Robert Fowler, and went insane in 1799.