Oliver St John of Bletsoe, 1st Baron St John of Bletso (c. 1522 – 21 April 1582) was an English peer. He was the son of Sir John St John (born 1498) of Bletsoe and Spelsbury and his first wife Margaret, the daughter of Sir William Waldegrave. His paternal great-great-great-grandfather Sir Oliver St John of Bletsoe, Spelsbury and Lydiard Tregoze (d. 1437) was the husband of Margaret Beauchamp of Bletso, great-great-granddaughter of Roger de Beauchamp, who was summoned to Parliament as Baron Beauchamp of Bletso from 1363 to 1379. Since then that title had not been assumed, although St John was considered to be the line of heir. On 13 January 1559 he was raised to the peerage himself as Baron St John of Bletso, in the county of Bedfordshire.