Sir John Trelawny, 1st Baronet (24 April 1592 – 16 February 1664) was a Cornish baronet and soldier from Trelawne, Cornwall. He was High Sheriff of Cornwall.
John Trelawny was born in Hall, near Fowey in Cornwall on 24 April 1592, and baptised in Fowey on 7 May. He was the eldest son of Jonathan Trelawny and Elizabeth Killigrew. He studied at Merton College, Oxford where he matriculated 23 October 1607.
In 1628, Trelawny became involved in the dispute between Charles I and leading members of Parliament which eventually led to the English Civil War. The King was anxious to influence the election of MPs so as to secure a more pliable Parliament, and in Cornwall efforts on his behalf were being directed by one James Bagg, acting in concert with the Duke of Buckingham. Two of the King's most implacable opponents, William Coryton and Sir John Eliot, had announced their intention of standing for election as knights of the shire for Cornwall, and Bagg arranged for a caucus of influential Cornish magistrates to mobilise against them. They not only used the official posts to promote alternative candidates and attempted to instruct the High Sheriff (Trelawny himself was High Sheriff of Cornwall in 1630) who he should return as elected, but they wrote open letters to the freeholders of the county appealing that they should not elect Coryton or Eliot, and to Eliot and Coryton themselves, warning them against persisting with their candidacy. These letters were signed by all the magistrates concerned, of whom Trelawny was one.
The campaign was unavailing, and Eliot and Coryton were duly elected. But such means of campaigning were not then considered legitimate, and when Parliament met the House of Commons issued summonses to all those who had signed the letters, demanding that they appear at the bar of the House and explain themselves. When they failed to attend, Trelawny and three of the others were arrested and brought to London. After hearing counsel's arguments on both sides, the House committed Trelawny and another offender, Walter Langdon, to the Tower of London, both for the original offence and for their contempt of Parliament in failing to answer the summons.