Which French marshal later became King of Sweden?

The French marshal who later became King of Sweden was Jean-Baptiste Bernadotte.

Born in Pau, France, in 1763, Bernadotte rose rapidly through the French Revolutionary armies. Napoleon made him a Marshal of the Empire in 1804, recognizing his military service despite their sometimes tense relationship. Bernadotte also became Prince of Pontecorvo, a title created by Napoleon in 1806.

In 1810, Sweden unexpectedly selected Bernadotte as crown prince and heir to the childless King Charles XIII. He adopted the name Charles John and eventually became King Charles XIV John of Sweden in 1818. He founded the Bernadotte dynasty, which remains Sweden's royal house.

Bernadotte's later career took him away from Napoleon. During the final coalition wars, he allied with Russia and commanded the Allied Army of the North against France. The other options were also prominent French commanders, but Michel Ney, Davout, and Murat did not become kings of Sweden.