FREDERICK IV. (1574-1610), elector palatine of the Rhine, only surviving son of the elector Louis VI., was born at Amberg on the 5th of March 1574. His father died in October 1583, when the young elector came under the guardianship of his uncle John Casimir, an ardent Calvinist, who, in spite of the wishes of the late elector, a Lutheran, had his nephew educated in his own form of faith. In January 1592, on the death of John Casimir, Frederick undertook the government of the Palatinate, and continued the policy of his uncle, hostility to the Catholic Church and the Habsburgs, and co-operation with foreign Protestants. He was often in communication with Henry of Navarre, afterwards Henry IV. of France, and like him was unremitting in his efforts to conclude a league among the German Protestants, while he sought to weaken the Habsburgs by refusing aid for the Turkish War. After many delays and disappointments the Union of Evangelical Estates was actually formed in May 1608, under the leadership of the elector, and he took a prominent part in directing the operations of the union until his death, which occurred on the 19th of September 1610. Frederick was very extravagant, and liked to surround himself with pomp and luxury. He married in 1593 Louise, daughter of William the Silent, prince of Orange, and was succeeded by Frederick, the elder of his two sons. See M. Ritter, _Geschichte der deutschen Union_ (Schaffhausen, 1867-1873); and L. Haeusser, _Geschichte der rheinischen Pfalz_ (Heidelberg, 1856).