Charlemagne was succeeded in 814 by his son, Louis the Pious (778-840). He built coastal defences against the Viking raids which had begun during his father's reign. The Vikings, mainly from Denmark, were to continue harrying the coastal areas of the Netherlands for at least another 200 years, sailing up the rivers to plunder deep inland.

Following the death of Louis the Pious, the empire was divided between his three sons by the Treaty of Verdun (843). The eldest, Lothair, was given the imperial crown and the extensive middle kingdom stretching from central Italy to the North Sea and incorporating the Low Countries. On his death, this middle kingdom was further divided between his own three sons. The northern part, Lotharingia, which extended from Friesland to the Jura in eastern France, fell to Lothair II, from whom it got its name. After Lothair II died leaving no legitimate heirs, Lotharingia was partitioned into the west and east Frankish kingdoms. In 925, however, King Henry (the Fowler) of Germany conquered the whole of Lotharingia. From then until 1648, the Netherlands was to remain officially part of the German-ruled Holy Roman Empire, despite constant efforts to regain its independence.

The feudal system in the Holy Roman Empire had a profound effect on the social structure of the area. The spiritual and temporal lords were bound as vassals, or liegemen, to the king, from whom they received fiefs in return for their fealty. The lords in their turn granted their vassals land in fief. At the base of the pyramid were the peasants or serfs, who were allowed small pieces of land but had to surrender most of what they produced to their overlords. In the course of time, the vassals began to act more independently of the empire and so laid the foundations for the earliest counties (lands ruled by a count) and later for the independent principalities. The term 'Holland' emerged around 1100 as the name of one such county.

During this period of fragmentation of power, much land was brought into cultivation and trade and industry increased. As a result, the proportion of the population living in towns increased substantially. This in turn made the municipal authorities more important. The power of the Emperors was increasingly undermined by the push for independence by the counts and their vassals. They tried to restore it by investing loyal Churchmen with temporal powers and loyal secular lands with ecclesiastical powers. This strategy led to the investiture controversy between the Holy Roman Emperor and the Pope in the eleventh and twelfth centuries. The contest finally ended in 1122 when the Emperor renounced his claim to influence over the appointment of bishops and abbots. This reduction in the Emperor's power ushered in a further decline of the Holy Roman Empire.