FREDERICK III. (1515-1576), called "the Pious," elector palatine of the Rhine, eldest son of John II., count palatine of Simmern, was born at Simmern on the 14th of February 1515. In 1537 he married Maria (d. 1567), daughter of Casimir, prince of Bayreuth, and in 1546, mainly as a result of this union, adopted the reformed doctrines, which had already made considerable progress in the Palatinate. He lived in comparative obscurity and poverty until 1557, when he became count palatine of Simmern by his father's death, succeeding his kinsman, Otto Henry (1502-1559), as elector palatine two years later. Although inclined to the views of Calvin rather than to those of Luther, the new elector showed great anxiety to unite the Protestants; but when these efforts failed, and the breach between the followers of the two reformers became wider, he definitely adopted Calvinism. This form of faith was quickly established in the Palatinate; in its interests the "Heidelberg Catechism" was drawn up in 1563; and Catholics and Lutherans were persecuted alike, while the churches were denuded of all their ornaments. The Lutheran princes wished to root out Calvinism in the Palatinate, but were not willing to exclude the elector from the benefits of the religious peace of Augsburg, which were confined to the adherents of the confession of Augsburg, and the matter came before the diet in 1566. Boldly defending his position, Frederick refused to give way an inch, and as the Lutherans were unwilling to proceed to extremities the emperor Maximilian II. could only warn him to mend his ways. The elector was an ardent supporter of the Protestants abroad, whom, rather than the German Lutherans, he regarded as his co-religionists. He aided the Huguenots in France and the insurgents in the Netherlands with men and money; one of his sons, John Casimir (1543-1592), took a prominent part in the French wars of religion, while another, Christopher, was killed in 1574 fighting for the Dutch at Mooker Heath. In his later years Frederick failed in his efforts to prevent the election of a member of the Habsburg family as Roman king, to secure the abrogation of the "ecclesiastical reservation" clause in the peace of Augsburg, or to obtain security for Protestants in the territories of the spiritual princes. He was assiduous in caring for the material, moral and educational welfare of his electorate, and was a benefactor to the university of Heidelberg. The elector died at Heidelberg on the 26th of October 1576, and was succeeded by his elder surviving son, Louis (1539-1583), who had offended his father by adopting Lutheranism. See A. Kluckhohn, _Friedrich der Fromme_ (Noerdlingen, 1877-1879); and _Briefe Friedrichs des Frommen_, edited by Kluckhohn (Brunswick, 1868-1872).