On February 13, 1575, a unique situation occurred in the history that the King of Poland was crowned King of France. It was Henry III. from the Capet-Valois dynasty. Namely, he was in the reign of his older brother King Charles IX. elected from France as king of Poland (in Poland, the royal throne was in principle not inherited but elected by the king). Thus, Henry III. became king of Poland in 1573 and was crowned in Krakow the following year. In France at that time, as king’s brother, he held the title of Duke of Anjou.
Since Henry’s brother, the aforementioned King Charles IX, died without descendants, Henry III. succeeded him. In doing so, he united the crowns of Poland and France. He was anointed and crowned in Reims, the traditional crowning site of the French rulers. The Polish Parliament decided that Henry III. to lose the Polish throne if he did not return to Poland by 12 May 1575. Indeed, he did not return to the country, so the Polish throne was declared vacant. In France, Henry III. continued to rule until 1589. Interestingly, in 1578 he founded the famous Order of the Holy Spirit (French L’Ordre du Saint-Esprit) as the highest French knightly order.