John Casimir, Duke of Saxe-Coburg

), was a duke of Saxe-Coburg.

He was the third but eldest surviving son of Johann Frederick II, Duke of Saxony and Elisabeth of the Palatinate-Simmern-Sponheim.

After the "Reichsexekution" against Gotha in 1567 the father lost his lands and his liberty. Afterwards, Johann Casimir, as well as his older brother Frederick Heinrich (who died in 1572 aged 11), his younger brother, Johann Ernst, and their mother, lived firstly in Eisenach, later at the "Hofe" (castle) of his uncle Johann Wilhelm in Weimar, and finally in Eisenberg.

In 1570, during the Diet of Speyer the sons tried to recovered their hereditary rights. Later, their mother left him and his brothers and moved to Austria, while the Partition Treaty (Division of Erfurt, 1572) with his uncle Johann Wilhelm was made. The two brothers received the "Duchy of Saxe-Coburg-Eisenach": This principality consisted in the towns of Gotha and Hildburghausen and Eisenach, on the south and west Thuringian areas. Guardians of the children were Johann George, Elector of Brandenburg, his maternal grandfather Frederick III, Elector Palatine, and Augustus, Elector of Saxony. From 1578 to 1581 Johann Casimir studied in the University of Leipzig.

In 1584 he became engaged to Anna of Saxony, the daughter of Elector Augustus; the marriage took place two years later (16 January 1586) in the city of Dresden. Only after the death of his father-in-law (11 February 1586) were Johann Casimir (aged 22) and his brother Johann Ernst able take full control of their principalities.

In 1596 Johann Casimir and Johann Ernst divided their principalities: Johann Ernst took the "Duchy of Saxe-Eisenach" and Johann Casimir continued to govern in Coburg alone. His area of rule consisted of: Coburg, Rodach, Gestungshausen, Heldburg, Hildburghausen (1/2), Römhild, Eisfeld, Schalkau, Sonneberg, Neustadt, Neuhaus, Mönchröden and Sonnefeld.

Under Johann Casimir's reign the Coburg state experienced a cultural boom with much building activity. These buildings can still be visited today. The Schloss Ehrenburg was converted into a Renaissance castle, and he established the Veste Coburg as the national fortress and the arsenal as well as the government building in the market place. In the "Morizkirche" (Church of Saint Moritz) Johann Casimir built a twelve meter high alabaster tomb set for his parents in 1598, which is ranked among the most beautiful Renaissance Tombs in Germany. He also created in 1601 the "Gymnasium Casimirianum" (Casimirianum High School), extended the library of his castle with the inherited book inventories and, in 1603, he chosen the composer Melchior Franck as his "Hofkapellmeister" (High Music Master of Chapel).

Politically he was able to assure the nobility of the realm jurisdiction on their lands. He issued a church edict for the Lutheran regional church with the duke as "Summus Episcopus", which was later adopted by many other Thuringian states. In 1589 he established own authorities for the Law and the Church in Coburg: the "Hofgericht" (special court for noblemen), "Appellationsrat" (court of Appellations), "Schoeppenstuhl" (Court of Justice) and 1593 a "Konsistorium". Above all, he established an administrative machinery that existed after his death for many years and survived many political changes. He was able to remain neutral until 1629 in the Thirty Years' War. After his entry into the Swedish Alliance in 1632, the imperial and Bavarian troops invaded Coburg and tried, unsuccessfully, to seize the Veste. Johann Casimir fled in time to Thuringia.

During his rule the witch trials and burnings in Coburg had their high point. In 1593 Johann Casimir caught his wife in adultery and obtained the annulment of his marriage; Anna was kept imprisoned in the Veste Coburg until her death in 1613. In Coburg on 16 September 1599, Johann Casimir married secondly with Margarethe of Brunswick-Lüneburg.

After the death of Johann Casimir without heirs, his inheritance fell to his younger brother, Johann Ernst of Saxe-Eisenach.