Who was most responsible for making French the national language of France?

The establishment of French as the national language of France can largely be attributed to the efforts of King Francis I in the 16th century. His Edict of Villers-Cotterêts in 1539 mandated the use of French in legal documents and official communications, effectively promoting its use over Latin. This initiative was part of a broader movement to unify the country and strengthen royal authority, contributing significantly to the rise of French as a national language. Subsequent efforts in education and administration further cemented its status throughout the centuries.