Charlemagne judges the accusations against Pope Leo III in the Vatican.

Charlemagne ( SHAR-lə-mayn, -⁠MAYN, French: [ʃaʁləmaɲ]) or Charles the Great (Latin: Carolus Magnus; German: Karl der Große; 2 April 747 – 28 January 814), a member of the Carolingian Dynasty, was King of the Franks from 768, King of the Lombards from 774, and the first Holy Roman Emperor from 800. Charlemagne succeeded in uniting the majority of western and central Europe and was the first recognized emperor to rule from western Europe since the fall of the Western Roman Empire around three centuries earlier. The expanded Frankish state that Charlemagne founded was known as the Carolingian Empire. He was later canonized by Antipope Paschal III— later treated as invalid—and he is now regarded as beatified (which is a step on the path to sainthood) by the mainstream Catholic Church.

Charlemagne was the eldest son of Pepin the Short and Bertrada of Laon. He was born before their canonical marriage. He became king of the Franks in 768 following his father's death, and was initially as co-ruler with his brother Carloman I until the latter's death in 771. As sole ruler, he continued his father's policy towards protection of the papacy and became its sole defender, removing the Lombards from power in northern Italy and leading an incursion into Muslim Spain. He also campaigned against the Saxons to his east, Christianizing them (upon penalty of death) and leading to events such as the Massacre of Verden. He reached the height of his power in 800 when he was crowned Emperor of the Romans by Pope Leo III on Christmas Day at Old St. Peter's Basilica in Rome.

Charlemagne has been called the "Father of Europe" (Pater Europae), as he united most of Western Europe for the first time since the classical era of the Roman Empire and united parts of Europe that had never been under Frankish or Roman rule. His rule spurred the Carolingian Renaissance, a period of energetic cultural and intellectual activity within the Western Church. The Eastern Orthodox Church viewed Charlemagne less favourably due to his support of the filioque and the Pope's having preferred him as emperor over the Byzantine Empire's first female monarch, Irene of Athens. These and other disputes led to the eventual later split of Rome and Constantinople in the Great Schism of 1054.Charlemagne died in 814. He was laid to rest in the Aachen Cathedral, in his imperial capital city of Aachen. He married at least four times, and had three legitimate sons who lived to adulthood. Only the youngest of them, Louis the Pious, survived to succeed him. Charlemagne and his predecessors are the direct ancestors of many of Europe's royal houses, including the Capetian dynasty, the Ottonian dynasty, the House of Luxembourg and the House of Ivrea.