Esmonde, John (1760?–98), physician and United Irishman, was the second son in the family of three sons and four daughters of James Esmonde (1701–67) of Ballynastragh, near Gorey, Co. Wexford. As a young man James Esmonde was a French army officer but returned to Ireland on the death of his father, Laurence Esmonde (1676?–1760), and very briefly was 7th baronet in succession to his cousin, Sir Walter Esmonde (d. 1767). John Esmonde's mother was Ellice White, only daughter and heir of Thomas White of Pembrokestown, Co. Wexford. The eldest son, Thomas (1758–1803), inherited the baronetcy and property at an early age.
John Esmonde became a medical doctor, settled in Co. Kildare c.1783, became a member of the RCSI in March 1784 (shortly after its charter was granted) and in July 1785 married Helen, daughter and co-heiress of Bartholomew Callan or O'Callan of Osberstown, near Sallins. Callan had subscribed £5,000 to the setting up of the Bank of Ireland (1783). Helen had a personal fortune of £12,000 and much landed property. John Esmonde was to get a perpetual lease of Osberstown demesne (1794). His younger brother, James, was a distiller at Sallins; he married Anne, daughter of John Fitzgerald of Yeomanstown. As early as 1785, John Esmonde and his elder brother were listed as country members of the Catholic Committee. In March 1792 he was one of a delegation that presented a petition to the 2nd duke of Leinster (qv) seeking his support for the campaign for catholic relief; nine months later he attended the Catholic Convention in Dublin as one of six delegates from Co. Kildare; in February 1795 he was one of those Kildare gentry who petitioned the new lord lieutenant for further catholic relief.
Whether he was also associated with the Dublin Society of United Irishmen is unclear. When the Clane yeomanry cavalry corps was embodied in October 1796 under the command of Richard Griffith (qv), Esmonde became his first-lieutenant. But in 1798 Esmonde also associated with the United Irishmen in Co. Kildare, being appointed to their county committee and made treasurer (March 1798). The committee met (mid April) at his house at Osberstown to be briefed by John Sheares (qv). According to R. R. Madden (qv), it was to Esmonde that the final orders for the United Irish rebellion to begin on the night of 23 May were transmitted. According to Bernard Duggan, a United Irishman present at the rebel attack on the barracks at Prosperous on 24 May in which Capt. Richard Longueville Swayne and men of the North Cork militia was killed, it was Esmonde who directed the attack, though he remained at some distance and was ill informed of what was happening. After rejoining his yeomanry corps later in the day, perhaps believing his role at Prosperous had gone undetected and hoping to gather military intelligence or even to bring disaffected yeomen over to the rebel side, he was arrested at Naas on foot of information given to Griffith by Philip Mite, Esmonde's aide-de-camp on the rebel side and his sergeant in the yeomanry. Esmonde was sent to Dublin, tried, convicted and condemned by court martial. On the following day (14 June) he was hanged on Carlisle Bridge, reportedly with his yeoman's uniform turned inside out to symbolise his desertion and treason.
John and Helen Esmonde had five sons and one daughter. The eldest son, Thomas (1786–1868), succeeded his uncle as 9th baronet and was MP for Wexford borough (1841–7). The second became a priest. The fourth son, Laurence (1797–1884), was a colonel of grenadiers in the French army and married into the French aristocracy. Helen married, in 1802, another United Irish leader, Hervey Montmorency Morres (qv), and for many years defended the reputation of her first husband.