After the fall of the Western Roman Empire, the city of Genoa was invaded by Germanic tribes, and, in about 643, Genoa and other Ligurian cities were captured by the Lombard Kingdom under the King Rothari. In 773 the Kingdom was annexed by the Frankish Empire; the first Carolingian count of Genoa was Ademarus, who was given the title praefectus civitatis Genuensis. During this time and in the following century Genoa was little more than a small centre, slowly building its merchant fleet, which was to become the leading commercial carrier of the Western Mediterranean. In 934–35 the town was thoroughly sacked and burned by a Fatimid fleet under Ya'qub ibn Ishaq al-Tamimi. This has led to discussion about whether early tenth-century Genoa was "hardly more than a fishing village" or a vibrant trading town worth attacking.

In the year 958, a diploma granted by Berengar II of Italy gave full legal freedom to the city of Genoa, guaranteeing the possession of its lands in the form of landed lordships.] At the end of the 11th century the municipality adopted a constitution, at a meeting consisting of the city's trade associations (compagnie) and of the lords of the surrounding valleys and coasts. The new city-state was termed a Compagna Communis. The local organization remained politically and socially significant for centuries. As late as 1382, the members of the Grand Council were classified by both the companion to which they belonged as well as by their political faction ("noble" versus "popular").