Josias Rantzau (Bothkamp, near Kiel, 18 October 1609[1] – Paris, 14 September 1650[2]) was a Danish military leader and Marshal of France.
Josias was the grandson of Paul, the youngest son of Johann Rantzau.
He married his Cousin Hedwig Margarethe Elisabeth vor Rantzau, but had no children.[3]
As a young man, he served Prince Maurice of Orange and King Christian IV of Denmark.[4] Later he fought for Sweden, then the Holy Roman Empire, again for Sweden[5] and finally since 1635 for France, where he was noticed at Court for his blond beauty.
He commanded troops in the Franche-Comté,[6] on the Rhine,[6] and in Flanders. In 1633, he successfully defended Andernach against the Spanish,[7] but is in general better remembered for his bravery than for his military skills.