leading German theologian who was known, with reference to Martin Luther (Luther, Martin), as “the second Martin” and who helped unify the Lutheran church (Lutheranism) following the Reformation.

At the University of Wittenberg (1545), Chemnitz was the protégé of the Reformer Philipp Melanchthon (Melanchthon, Philipp). In 1550 at Königsberg (now Kaliningrad, Russia), he became librarian to Duke Albert of Prussia, an appointment that afforded him an opportunity to continue his theological studies. He returned to Wittenberg in 1553, entered the ministry as the pastor of the church of St. Aegidi, and began to lecture on Melanchthon's Loci communes rerum theologicarum (“Theological Commonplaces”), the first systematic treatise on Reformation theology. The following year Chemnitz became coadjutor to Joachim Mörlin, whom he succeeded in 1567 as superintendent of the churches of Braunschweig, a post he held for the rest of his life.

In 1568 he began a decade of work with the theologian Jakob Andreä in uniting German Lutheranism, which had been divided by theological disagreement after Luther's death in 1546. This end was achieved by the Formula of Concord (1577), which inaugurated the era of Lutheran orthodoxy and was primarily the work of the two men.

Chemnitz's works include a defense of the Lutheran doctrine of the real presence of Christ's body and blood in the Eucharist (1561); a systematic discussion of the relation between the divine and human natures of Christ (1570); Examen concilii tridentini (1565–73; Examination of the Council of Trent), the standard Lutheran analysis of the doctrinal decisions of the Council of Trent (Trent, Council of) (1545–63); and a partial presentation of his theology in the form of a commentary on Melanchthon's Loci communes (1591).