Johan Rantzau (12 November 1492 – 12 December 1565) was a German-Danish field marshal and statesman known for his role in the Count's Feud.

From his early years he sought a military career and was educated an officer and a mercenary (landsknecht), but at the same time he also acted as an important political advisor of the duke.

An attempt at conquering Funen in 1534 ended in a defeat and a humiliating retreat, but in the same year Rantzau crushed Skipper Clement's peasant rebellion in Jutland and secured the peninsula for the king.

[4] After the war, Rantzau continued being the king’s general and advisor, but he was pushed into the background in Denmark while concentrating on Holstein affairs.

In 1545 he resigned as the governor of Schleswig and Holstein in protest against the threefold division of the duchies between King Christian III and his brothers John the Elder and Adolf the year before.