Charlemagne, known as the "King of the Franks," ruled from 768 to 814 AD and was a key figure in the early Middle Ages. He united much of Western Europe during his reign, expanding the Frankish empire through military conquests and strategic alliances. Charlemagne was crowned Emperor of the Romans by Pope Leo III in 800 AD, marking the revival of the title in Western Europe after centuries. He promoted learning, culture, and the arts, initiating what is often referred to as the Carolingian Renaissance. His legacy significantly influenced the development of European nations and laid the foundation for the future Holy Roman Empire.