Pack, Sir Denis (1775–1823), British army general, was born 7 October 1775 in Kilkenny city, younger son of Rev. Thomas Pack (1720?–1795), dean of Ossory, and Catherine Pack (née Sullivan), of St Andrew's parish, Dublin. In June 1790 he entered TCD, aged 15, but did not take his degree. His elder brother, Thomas Pack, had previously attended TCD, but had died in December 1786.
Denis entered the army in November 1791, being commissioned as a cornet in the 14th Light Dragoons, and served with this regiment in Flanders in 1794 as part of Lord Moira's (qv) expedition. Transferring to the 8th Light Dragoons, he was promoted to lieutenant (March 1795) and took part in the expedition to Quiberon Bay. He was promoted to captain in February 1796 and served with the 5th Dragoon Guards in Ireland during the rebellion of 1798. Promoted to major (August 1798), he was attached to the 4th Royal Irish Dragoon Guards, and after the surrender of the French expeditionary force at Ballinamuck (8 September 1798) he commanded the troop that escorted Gen. Humbert (qv) and the other French officers to Dublin.
Promoted to lieutenant-colonel (December 1800), he commanded the 71st Highlanders and took part in the expedition to the Cape of Good Hope in 1806. He then took part in Gen. Whitelocke's expedition to South America and was captured after an unsuccessful attack on Montevideo. His fellow-prisoner was William Carr Beresford (qv), later 1st Viscount Beresford, and the two men remained friends for the rest of their lives. Refusing to give their parole to Gen. Liniers, they escaped from La Plata in a boat, meeting a British cruiser at sea. Pack later took part in the successful attack on Montevideo (9 February 1807).
He was posted to Portugal in 1808 and was present at the battles of Roliça (17 August) and Vimiera (21 August). In 1809 he took part in the Walcheren expedition and, promoted to colonel (July 1810), he was made ADC to George III. Returning to Portugal in 1810, he served under Beresford, commanding a Portuguese brigade, and took part in the battle of Busaco (27 September 1810). Promoted to brigadier-general in January 1812, he took part in the siege of Ciudad Rodrigo and was present at the battle of Salamanca (22 July 1812). In June 1813 he was promoted to major-general and later was present at the battles of Vittoria (21 June 1813), Nivelle (10 November 1813), Nive (10–13 December 1813), Orthes (27 February 1814) and the final French defeat at Toulouse (10 April 1814). In January 1815 he was made a KCB in recognition of his services in the Peninsula.
During the Waterloo campaign (1815), he commanded one of the brigades in Gen. Sir Thomas Picton's division. Present at the battle of Quatre Bras (16 June), he played a prominent part in the battle of Waterloo, bringing his brigade forward at a crucial moment to stop the advance of the French 3rd Division under Gen. Marcognet. During the course of his career he was wounded several times and was awarded numerous honours including the Peninsular Gold Cross (with seven clasps), the Order of the Tower and Sword (Portugal) and the Order of St Vladimir (Russia). In 1819 he was appointed governor general of Plymouth, and was later made honorary colonel of the 84th Foot (1822).
He married (July 1816) Lady Elizabeth Louisa de la Poer Beresford, daughter of George (1735–1800), 1st marquess of Waterford, and half-sister to Lord Beresford; they had two sons and two daughters. His descendants adopted ‘Pack-Beresford’ as their family name. He died 24 July 1823 at Lord Beresford's house in Upper Wimpole St., London. A monument to him was later erected in St Canice's cathedral, Kilkenny. A portrait by G. L. Saunders is in family possession; another by Charles Turner, showing Pack wearing his numerous orders and decorations, is in the National Portrait Gallery, London. A collection of his papers is held by the University of Southampton.