John Udall (yōō´dəl, yōōv´dāl), 1560?–1592, English clergyman, educated at Cambridge. He adopted Puritan sympathies and aided John Penry in issuing the anticlerical pamphlets published under the pseudonym Martin Marprelate. Udall was responsible for two tracts (1588) denouncing the episcopacy, The State of the Church of England and A Demonstration of the Truth. In 1590 he was arrested, charged with the authorship of the pamphlets, and sentenced to death. He was pardoned but died in prison shortly thereafter. His well-known Key to the Holy Tongue, a Hebrew grammar and dictionary, was published posthumously in 1593.