Luther's close connection with Gotha seems to have commenced during his student days at the University of Erfurt.
One of his fellow students, law student Justus Jonas, writes that Luther purchased his textbooks in Gotha. Returning, he met a "terrifying heavenly sight" that he interpreted as a call to be a monk. Getting back to Erfurt he said goodbye and joined himself to the Augustinian cloister in Erfurt in order to become a monk.
In May 1515, Luther spent some time in the town, something that would repeat itself often before his final visit in 1540. Not only did he come to the city to visit the Augustinian monastery, but also to rest on his way to Worms, Marburg, and Schmalkalden.
The German Augustinian congregation elected Luther District Vicar of the Augustinian Hermits for 11 years running, which brought the Great Reformer to the city many times.
As a young reformer on his way from Wittenberg to the Reichstag in Worms in 1521, he preached in the Augustinerkirche (St. Augustine's Church) several times with great sympathies within the population. It did not take long before the priest in the Margaretenkirche (St. Margaret's Church), Johann Langenhan, proclaimed the new teaching from the pulpit in 1522. This date marks the beginning of the Reformation in Gotha.
A few months after the so-called Gotha “Pfaffensturm” (a successful attack on the institution of the church), which was directed against the ruling conditions in the Catholic church, Friedrich Myconius was called to be the first evangelical pastor in Gotha in August, 1524.
Today, visitors can still visit the Luther House on the market square where Luther stayed on his way back from the “Princely Council” in Schmalkalden on 27 February 1537. Bed-ridden due to severe kidney pain, Luther stayed in the former guest house until 4th May; believing he would die, he used this time to dictate his last will and testament – the so-called Gotha Testament – to friend and fellow reformer, Johannes Bugenhagen. He even expressed the desire to his friend Myconius that he wanted to be buried here in Gotha and not in Wittenberg. Due to his recovery and return to Wittenberg, however, this desire remained unfulfilled.
Gotha’s St. Margaret’s Church was the first to convert to Protestantism in 1522; today, two impressive statues of Martin Luther and Phillip Melanchthon welcome visitors at the gates of the church that brought the Reformation to Gotha.
The Gotha Research Library is also located in the Friedenstein Castle. Its unique inventory of manuscripts, old prints, correspondence, diaries and inheritances has the rank of a reference collection for the history of Central-German Protestantism from the 16th through the 18th centuries. Numerous original documents that were written by Luther, Melanchthon and Calvin as well as other famous reformers from Central Germany and Europe are stored there. These manuscripts were collected on the order of the Dukes of Saxony-Gotha-Altenburg; most notably on the occasion of the 200th anniversary of the Reformation in 1717 by the Lutheran-Orthodox theologian Ernst Salomon Cyprian, who turned the library into an early centre of Reformation research.