HEYLYN (or HEYLIN), PETER (1600-1662), English historian and controversialist, was born at Burford in Oxfordshire. Having made great progress in his studies, he entered Hart Hall, Oxford, in 1613, afterwards joining Magdalen College; and in 1618 he began to lecture on cosmography, being made fellow of Magdalen in the same year. His lectures, under the title of [Greek: Mikrokosmos], were published in 1621, and many editions of this useful book, each somewhat enlarged, subsequently appeared. Having been ordained in 1624 Heylyn attracted the notice of William Laud, then bishop of Bath and Wells; and in 1628 he married Laetitia, daughter of Thomas Highgate, or Heygate, of Hayes, Middlesex; but he appears to have kept his marriage secret and did not resign his fellowship. After serving as chaplain to Danby in the Channel Islands, he became chaplain to Charles I. in 1630, and was appointed by the king to the rectory of Hemingford, Huntingdonshire. John Williams, bishop of Lincoln, however, refused to institute Heylyn to this living, owing to his friendship with Laud; and in return Charles appointed him a prebendary of Westminster, where he made himself very objectionable to Williams, who held the deanery _in commendam_. In 1633 he became rector of Alresford, soon afterwards vicar of South Warnborough, and he became treasurer of Westminster Abbey in 1637; but before this date he was widely known as one of the most prominent and able controversialists among the high-church party. Entering with great ardour into the religious controversies of the time he disputed with John Prideaux, regius professor of divinity at Oxford, replied to the arguments of Williams in his pamphlets, "A Coal from the Altar" and "Antidotum Lincolnense," and was hostile to the Puritan element both within and without the Church of England. He assisted William Noy to prepare the case against Prynne for the publication of his _Histriomastix_, and made himself useful to the Royalist party in other ways. However, when the Long Parliament met he was allowed to retire to Alresford, where he remained until he was disturbed by Sir William Waller's army in 1642, when he joined the king at Oxford. At Oxford Heylyn edited _Mercurius Aulicus_, a vivacious but virulent news-sheet, which greatly annoyed the Parliamentarians; and consequently his house at Alresford was plundered and his library dispersed. Subsequently he led for some years a wandering life of poverty, afterwards settling at Winchester and then at Minster Lovel in Oxfordshire; and he refers to his hardships in his pamphlet "Extraneus Vapulans," the cleverest of his controversial writings, which was written in answer to Hamon l'Estrange. In 1653 he settled at Lacy's Court, Abingdon, where he resided undisturbed by the government of the Commonwealth, and where he wrote several books and pamphlets, both against those of his own communion, like Thomas Fuller, whose opinions were less unyielding than his own, and against the Presbyterians and others, like Richard Baxter.