John Barwick (1612–1664) was an English royalist churchman and Dean of St. Paul's Cathedral.
He was born at Witherslack, in Westmorland. John was the third of five sons, and he and his brother Peter Barwick (later his biographer) were the ones given an education. After time at local grammar schools John was sent to Sedbergh School, then in Yorkshire. In 1631 he entered St. John's College, Cambridge, where Thomas Fothergill was his tutor, and graduated B.A. in 1635. The Master Owen Gwyn had died in 1634, and the subsequent election was disputed and attracted the attention of the king; Barwick became involved as the college’s representative. He was then elected to a fellowship. He took holy orders, and in 1638 his M.A. degree.
In 1642 royalists at Cambridge raised a sum of money for the king, and gathered together some college plate. Parliament received information of what was going on, and sent Oliver Cromwell with a party of infantry to a place called Lower Hedges, on the road between Cambridge and Huntingdon. A party of horse was formed under Barnabas Oley of Clare College, of which Barwick was one, who conveyed the treasure along back roads to Nottingham. Subsequently, Cromwell moved on Cambridge, taking over the castle. Two pamphlets were put together by Cambridge academics against Cromwell: the first was by Barwick with Isaac Barrow, Peter Gunning, and Samuel Ward; the second is attributed to Barwick alone.
Barwick left Cambridge, and became chaplain to Bishop Thomas Morton, who nominated him to a prebend at Durham Cathedral and the rectories of Houghton-le-Spring and Walsingham; Barwick in fact settled in London, since Morton at the time had no effective patronage. At Durham House Barwick undertook royalist correspondence and intelligence work, and tried to make converts of some parliamentarians. He worked for the Treaty of Newport of 1648, and was supported by his brothers Peter and Edward. In the end he was betrayed by a post-office official, and Barwick had to destroy his ciphers while arresting officers were breaking into his room. He was charged with high treason, and was committed (April 1650) first to the Gatehouse prison at Westminster, and then to the Tower of London. He was released, without any trial but in much better health, in August 1652.