Charlemagne, or Charles the Great (742–814), a king of the Franks and the founder of an empire that included much of western Europe. The establishment of his empire marked the shift of power in western Europe from the Mediterranean area to the north. By bringing much of western Christendom under one rule, Charlemagne was able to establish order and maintain peace during his lifetime. By establishing a network of royal administrators with authority over local taxes, courts, and churches, he strengthened the central authority of the king over his vassals and provided a set of unwritten but fairly uniform laws for the entire kingdom. At the same time the Christian church was organized on a firm and lasting basis throughout his realm.

Charlemagne was a patron of scholars and an enthusiastic supporter of learning. His scriptoria (book-copying establishments) preserved for later ages many of the works of the past. Schools were established throughout the empire for the training of priests. At his own home he established the Palace School for the sons of nobility who flocked to his court. Although many of these schools were destroyed in the long period of anarchy that followed his death, western Europe was never as dark after his day as it had been before.

Charlemagne was born at Aix-la-Chapelle (the French name for the German city of Aachen). He was a son of Pepin the Short, king of the Franks, and a grandson of Charles Martel. After Pepin's death in 768, his kingdom was divided, according to custom, between his sons; Charlemagne received the northern part and his younger brother Carloman, the southern part. After Carloman died in 771 Charlemagne made himself ruler of the whole area.

Charlemagne extended his territory until it included the greater part of western Europe. He organized military campaigns both to subdue rebellious nobles within his inherited kingdom and to conquer neighboring realms, leading many of the campaigns himself. He conquered the Lombards in Italy and routed the Saracens in northeastern Spain. (The medieval tale Chanson de Roland is loosely based on the events of the Spanish expedition.) In a long series of bloody campaigns, Charlemagne finally overcame the Saxons as far north as the Elbe and the Baltic. He also conquered the Avars, a Mongol tribe inhabiting the Danube valley.

Charlemagne's conquests not only expanded the Frankish kingdom and its tributary lands, but also increased the domain of the Christian church. Wherever his armies were victorious, the people were converted and monasteries were built.

In Rome, on Christmas Day, 800, Pope Leo III crowned Charlemagne emperor of Rome. This coronation was a symbolic gesture intended to increase the power of Charlemagne (and, through him, the power of the pope) by claiming for him the inheritance of ancient Roman authority. It created, in theory, two rulers of western Europe—the emperor and the pope. Wherever the banners of the empire flew, the church was to find protection. Wherever the doctrines of the Roman church were accepted, the authority of the empire was to be recognized. This theory outlived Charlemagne's own empire and did not die until the final breakup of the Holy Roman Empire in 1806.

Charlemagne's capital and favorite residence was Aix-la-Chapelle. Here he built a magnificent palace and a noble marble cathedral, or chapelle.

Charlemagne's son, Louis the Pious, succeeded to the throne after his father's death. After Louis' death in 840 his three sons (Charles, Lothair, and Louis) fought over the empire and by the Treaty of Verdun (843) divided it among themselves. This empire was never reunified. Although Charlemagne is often considered the first Holy Roman emperor, there was no real connection between his empire and the Holy Roman Empire, which was established by Otto I in 962.