By 500 AD, the Franks , who gave their name to modern France, had become the dominant invading power. Their most celebrated king, Clovis , consolidated his hold on northern France and drove the Visigoths out of the southwest into Spain. In 507 he made the until-then insignificant little trading town of Paris his capital and became a Christian, which inevitably hastened the Christianization of Frankish society.

Under the succeeding Merovingian - as the dynasty was called - rulers, the kingdom began to disintegrate until in the eighth century the Pepin family, who were the Merovingians' chancellors, began to take effective control. In 732, one of their most dynamic scions, Charles Martel , reunited the kingdom and saved western Christendom from the northward expansion of Islam by defeating the Spanish Moors at the battle of Poitiers .

In 754 Charles's son, Pepin, had himself crowned king by the pope, thus inaugurating the Carolingian dynasty and establishing for the first time the principle of the divine right of kings. His son was Charlemagne , who extended Frankish control over the whole of what had been Roman Gaul, and far beyond. On Christmas Day in 800, he was crowned emperor of the Holy Roman Empire , though again, following his death, the kingdom fell apart in squabbles over who was to inherit various parts of his empire. At the Treaty of Verdun in 843, his grandsons agreed on a division of territory that corresponded roughly with the extent of modern France and Germany.

Charlemagne's administrative system had involved the royal appointment of counts and bishops to govern the various provinces of the empire. Under the destabilizing attacks of Normans/Norsemen/Vikings during the ninth century, Carolingian kings were obliged to delegate more power and autonomy to these provincial governors , whose lands, like Aquitaine and Burgundy , already had separate regional identities as a result of earlier invasions - the Visigoths in Aquitaine, the Burgundians in Burgundy, for example.

Gradually the power of these governors overshadowed that of the king, whose lands were confined to the Île-de-France. When the last Carolingian died in 987, it was only natural that they should elect one of their own number to take his place. This was Hugues Capet, founder of a dynasty that lasted until 1328