Johannes Gerhard (17 October 1582 – 17 August 1637) was a Lutheran church leader and Lutheran Scholastic theologian during the period of Orthodoxy.
He was born in the German city of Quedlinburg. At the age of fourteen, during a dangerous illness, he came under the personal influence of Johann Arndt, author of Das wahre Christenthum, and resolved to study for the church. He entered the University of Wittenberg in 1599, and studied philosophy and theology. A relative then persuaded him to change his subject, and he studied medicine for two years. In 1603, he resumed his theological reading at Jena, and in the following year received a new impulse from J.W. Winckelmann and Balthasar Mentzer at Marburg. He graduated in 1605 and began to give lectures at Jena, then in 1606 he accepted the invitation of John Casimir, Duke of Coburg, to the superintendency of Heldburg, today Bad Colberg-Heldburg, and mastership of the gymnasium; soon afterwards he became general superintendent of the duchy, in which capacity he was engaged in the practical work of ecclesiastical organization until 1616, when he became the senior theological professor at Jena, where the remainder of his life was spent.
Here, with Johann Major and Johann Himmel, he formed the "Trias Johannea." Though still comparatively young, Gerhard was already regarded as the greatest living theologian of Protestant Germany; in the "disputations" of the period he was always protagonist, and his advice was sought on all public and domestic questions touching on religion or morals. During his lifetime he received repeated calls to almost every university in Germany (e.g. Giessen, Altdorf, Helmstedt, Jena, Wittenberg), as well as to Uppsala in Sweden. He died in Jena.