General the Honourable Henry St John (1738 – 3 April 1818) was a senior British Army officer and politician who sat in the House of Commons from 1768 to 1784 and briefly in 1802.

[2] His paternal grandparents were Henry St John, 1st Viscount St John and the former Angelica Magdalena (née Pellisary) Wharton, the widow of Philip Wharton who was the daughter of George Pellisary, Treasurer-General of the Navy to King Louis XIV of France.

His mother was the half-sister, and heiress, of Sir Henry Furnese, 3rd Baronet, and the only child, by his first wife Anna Balam (daughter of Anthony Balam), of Sir Robert Furnese, 2nd Baronet, MP for Truro, New Romney, and Kent.

In 1760 he was promoted Major in the 91st Regiment of Foot, made Lieutenant-Colonel in 1762 and put on half pay in 1763.

[3] He was elected Member of Parliament for Wootton Bassett in 1761, sitting until 1784 and again in 1802, vacating his seat the same year.