John III, Duke of Cleves and Count of Mark (German: Johann III der Friedfertige; 10 November 1490 – 6 February 1539), known as John the Peaceful, was the Lord of Ravensberg, Count of Mark, and founder of the United Duchies of Jülich-Cleves-Berg.

[1] In 1510, at the age of 19, John married Duchess Maria of Jülich-Berg,[2] daughter of Duke William IV of Jülich-Berg and Sibylle of Brandenburg, who became heiress to her father's estates Jülich, Berg and Ravensberg.

John represented a compensatory attitude, which strove for a via media between the two confessions during the Protestant Reformation.

In 1532 John wrote up a list of church regulations (Kirchenordnung), which expressed numerous ideas of Erasmus.

[3] John and his wife Duchess Maria of Jülich-Berg had the following children: John also had with an unknown woman; Elisabeth of Cleves (b.?- 15 July 1554) Married Gottfried von Bemmel, bailiff of Kervendonk and had issue.