Charlemagne (742 - 814) was King of the Franks from 768 to his death. He was at first co-ruler with his brother Carloman I to 771. When his brother died, Charlemagne refused the throne to his nephews and ruled the entire Frankish realm. He worked to re-establish his Kingdom as the main power in Western Europe. By 774, he managed to conquer the Lombards of Northern and Cental Italy and added the Lombard Crown to his own. His realm extended to areas currently held by Croatia.On December 25, 800 Pope Leo crowned him Emperor of the Romans. The title was held at the time by Irene, Byzantine Empress. The Papal and Frankish argument was that a woman could not rule and the Roman throne was vacant. Charlemagne had by then expanded his realm to include much of modern Germany and areas of Poland. An attempt to expand into Moorish Spain was a failure.

His reign saw a revival of art, religion and culture in Western Europe, largely as a result of his policies. He enforced Christianity in the areas he ruled and is responsible for the extinction of German pagan religions. Christianity also gained a foothold in Denmark through his diplomatic efforts. His reign is considered transitional from the barbaric "Dark Ages" to the more cultured "Middle Ages". His son Louis I the Pious succeeded him but the realm was later split among various grandchildren.