John Hensleigh Allen DL (29 August 1769 – 12 April 1843) was the Whig member of parliament for Pembroke elected at the 1818 United Kingdom general election until the 1826 United Kingdom general election. He was the son of (1733–1792) a local landowner and colliery owner and his first wife Elizabeth Hensleigh. He had 9 sisters, and his brothers-in-law included Josiah Wedgwood II, Sir James Mackintosh (both Whig MPs), John Wedgwood the horticulturist and Jean Charles Léonard de Sismondi the historian. He was High Sheriff of Pembrokeshire in 1809.