In 1384, Jadwiga of Poland who was just 10 years old at the time was crowned King of Poland. One thing though was the daughter of Louis I of Hungary and Elizabeth of Bosnia. So why was she not crowned Queen of Poland? Well, that is a whole story of political disputes and royal family drama. Born in Buda in Hungary, Jadwiga was raised in the royal court and was well educated. She spoke at least six different languages such as Serbian, Polish, German fluently including Latin. When her father died, her elder sister Mary did inherit the throne, but the Lords of Poland were not happy with this arrangement.
Mostly because Mary was already Queen of Hungary, so instead, they decided that Jadwiga would be a better choice. But Polish law did not have any provision for allowing Queens to rule, so the lords decided to simply crown her as King of Poland – after all the laws did not specify that the king had to necessarily be male. Given that she held the title of King, this meant that Jadwiga was a monarch in her own right and was not simply acting as a Queen consort until she married.
Eventually, she did marry the Grand Duke Jogaila of Lithuania at 12 years of age. This was to create a strong alliance between Poland, Lithuania, and Ruthenia to be able to resist the aggressive Russian and German expansions. Although most historians believe Jogaila would have handled most of the day to day politics, Jadwiga was a highly educated woman and there is much evidence that she did have various political and diplomatic roles within the kingdom.
For example, in 1387, she led several successful military expeditions into Hungary to defend their lands in Red Ruthenia. And she also was an integral part of their negotiations with the Teutonic Knights, along with helping Jogaila speak with the Lithuanian princes. Jadwiga also had a key part of growing Polish culture at the time, providing several donations to writers and artists. She also donated much of her wealth to many hospitals.