John III, Duke of Cleves (d. 1539)
John III, Duke of Cleves and Count of Mark (John III, Duke of Cleves; John I, Duke of Jülich-Berg; German: Johann III der Friedfertige, Herzog von Jülich-Kleve-Berg; 10 November 1490 – 6 February 1538 or 1539), called John the Peaceful, was a son of John II, Duke of Cleves and Mathilde of Hesse, daughter of Henry III, Landgrave of Upper Hesse.John III became Regent of the United Duchies of Jülich-Cleves-Berg in 1521, and Lord of Ravensberg in 1528.

John represented a compensatory attitude, which strove for a via media, a middle way, between the two confessions during the Protestant Reformation. Despite what others may have thought, not all Germanic princely houses were Lutheran Protestant. In fact the real influence at the court of Cleves was Erasmus. Many of his men were friends and followers of this well-educated Dutch scholar and theologian. When Duke John decided to write up a list of church regulations, Erasmus was the first person the Duke went to personally for consultation and approval.

Duke John had an instinct for balance as was shown when he married his eldest daughter Sybille to John Frederick of Saxony. John Frederick would go on to later head the Schmalkaldic League. In many ways, John of Cleves' court was ideal for raising a queen. It was fundamentally liberal, but serious-minded, theologically inclined, and profoundly Erasmian, as the court of Catherine of Aragon had once been. It was from this court that his daughter Anne would be raised. Anne would go on to marry King Henry VIII of England as his fourth wife.