Frederick III of Simmern, the Pious, Elector Palatine of the Rhine was a ruler from the house of Wittelsbach, branch PalatinateSimmernSponheim. He was a son of John II of Simmern and inherited the Palatinate from the childless Elector OttoHenry, Elector Palatine in 1559. He was a devout convert to Calvinism, and made Calvinism the official religion of his domain. Under his supervision the Heidelberg Catechism was constructed. His support of Calvinism gave the German Reformed movement a foothold within the Holy Roman Empire.
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Source: Wikipedia