Charles III of Spain

Born the fourth son of Philip V in 1716, Charles inherited the Duchy of Parma at 15, then at 18 led a nearly bloodless march down Italy to seize Naples and Sicily, where he ruled for 25 years and married Maria Amalia of Saxony, fathering 13 children. When his half-brother Ferdinand VI died childless in 1759, Charles took the Spanish crown and spent three decades applying what he'd learned: he modernized agriculture, strengthened the military, expelled the Jesuits, stripped American-born Spaniards of high office, and centralized control over the Church and colonies through new viceroyalties and intendancies. He reluctantly backed the American Revolution, even as his council floated the idea of peacefully cutting the empire loose to prevent revolt. He never fully controlled Spain's finances and sometimes borrowed to cover costs, but his reforms increased royal revenue and state power in ways that outlasted him, earning him a reputation as the most successful European ruler of his era.