Tennent, John (1772–1813), United Irishman and French soldier, was born 11 October 1772, sixth child and third son of the Rev. John Tennent, minister of the Seceding Presbyterian congregation of Roseyards, Ballymoney, Co. Antrim, and Anne Tennent (née Patton). Though 1772 was the year of his birth according to family records, French military archives give it as 1777. Educated at home by his father, he trained with a Coleraine merchant for a career in business. Radical politics in the later 1780s and early 1790s proved more attractive than business, however. Like his brother William (qv), only less cautiously, he became a United Irishman. After the failure of the French expedition to Bantry Bay (December 1796) and the increasingly vigorous measures taken against agitators by the government in Dublin, Tennent left Ireland in May 1797 and travelled to France by way of London, Hamburg, and The Hague. In 1799 he joined the French army as a volunteer, with the temporary rank of chef de bataillon, and saw service against the British.
In December 1803, when war resumed after the peace of Amiens, Tennent was appointed captain in a new Irish battalion. He was regarded as a good soldier and came to Napoleon's notice, representing his unit (along with William Corbet (qv)) at the emperor's coronation (2 December 1804) and receiving from him an eagle standard. Thereafter he served in Holland and Germany. In 1810 he was given command of a newly constituted battalion of the Irish Legion at Landau. He died in action against the Russians at Löwenberg in Germany on 19 August 1813. Two months earlier he had been nominated for the award of chevalier of the Legion of Honour, but it is unclear whether he received this award. He had married an unknown woman c.1802, who predeceased him. They had one child, a daughter named Frances (‘Fanny’). There is a portrait of him c.1810, by an unknown artist, in the Ulster Museum.