John Udall (also Udal or Uvedale) (1560?–1592) was an English clergyman of Puritan views, closely associated with the publication of the Martin Marprelate tracts, and prosecuted for controversial works of a similar polemical nature. He has been called "one of the most fluent and learned of puritan controversialists".
He matriculated as a sizar of Christ's College, Cambridge, on 15 March 1578, but soon afterwards migrated to Trinity College. There he graduated B.A. in 1581, and M.A. in 1584.John Penry was an undergraduate friend, and Udall also gained a working knowledge of Hebrew.
Before 1584 Udall took holy orders and became curate of Kingston-upon-Thames under the absentee vicar, Stephen Chatfield. He was soon known there as a preacher and a convinced Puritan doubter of the scriptural justification of episcopacy.
Although he gained a reputation and influential patrons, Udall's insistence on a literal observance of scriptural precepts was held to infringe the orthodoxy of the Church of England and in 1586 he was summoned by Thomas Cooper, bishop of Winchester and William Day, dean of Windsor to appear before the court of high commission at Lambeth. Through the influence of Anne, Countess of Warwick and Sir Drue Drury he was restored to his ministry.
The group that would launch Marprelate came together around this time. During 1587 Penry seems to have visited Udall at Kingston. The Puritan printer Robert Waldegrave was Penry's friend; it may be that in fact Udall made the introduction, though.
In April 1588 Udall induced Waldegrave to print at his office in London an anonymous and extreme tract in which Udall denounced the Church of England. In this work Diotrephes, named after a minor New Testament character, Udall waxed satirical, and the pamphlet gained public attention. It is close to the model of Anthony Gilby's A pleasaunt dialogue betweene a souldior of Barwicke and an English chaplaine (1581). The character Diotrephes is an anti-Puritan bishop; Udall himself rejected the identification as "Puritan", and the work contains his opinion that the term is from Satan via the papists, while he puts into the mouth of Diotrephes the view that Puritan applies to reformer of church government.