Polykarp Leyser the Elder, German theologian (d. 1610)
Polykarp (von) Leyser the Elder or Polykarp Leyser I (18 March 1552 – 22 February 1610) was a Lutheran theologian, superintendent of Braunschweig, superintendent-general of the Saxon church-circle, professor of theology at the University of Wittenberg and chief court-preacher and consistorial-councillor of Saxony.

Leyser was born in Winnenden. He married Elisabeth, the daughter of Lucas Cranach the Younger, and their children included Polykarp Leyser II (1586–1633), another theologian. This made him the founder of a dynasty of theologians, as great-grandfather of Polykarp Leyser III (1656–1725) and great-great-grandfather of Polykarp Leyser IV (1690–1728).

Supported by his father, his uncle Andreae and later his stepfather Osiander, and also with input from his teacher Martin Chemnitz, Leyser came to have an ingrained support for Lutheran orthodoxy – indeed, at a difficult time for Lutheranism, he was one of those who founded that orthodoxy. In the creative force of his Loci theologici (1591/92), Harmonia evangelica (1593), Postilla (1593) and De controversiis iudicium (1594), his theological position was forged by the dispute sparked by (Crypto-)Calvinism in Saxony, by the 'Exorzismusstreit', by the difficulties over Lutheran Christology and by Huber's debate. Leyser is thus to be accounted one of the key figures of the Lutheran concord in northern and central Germany and was constantly attacked in pamphlets as the 'pope of Dresden'. As one of the key movers behind the Formula of Concord, he used his books to defend Lutheran orthodoxy and attack Catholicism and Calvinism, was commissioned by the elector to join several of the meetings which led to the Book of Concord and advocated that the number of sponsors be limited to three people.

He wrote more than sixty theological works and an extensive corpus of sermons. He also dealt with the literary controversies of his time, cultivating an extensive correspondence of 200 written by him and 5000 written to him – an extensive selection from it was first published by his great-grandson Polycarp Leyser III as Sylloge epistolarum in 1706.