This thesis focuses on Lombard Southern Italy during the early middle ages and it analyses the history of political and social conflicts between the eighth and ninth century, taking into account the transformation of Lombard political power and social practices in this area. Starting from the eight-century judicial sources, this work explores political and social competition in the Beneventan region by taking into account its geographical position at the center of the Mediterranean see. Southern Italy was considered as a periphery, and sometimes as a frontier, by both the Carolingian and Byzantine empires, and endured almost a century of Muslims' attempts to conquer the peninsula. The first chapter focuses on the ducal period and investigates the formation and consolidation of the duke of Benevento's political authority before 774. During the seventh and eight centuries, the dukes developed a military and political autonomy in Southern Italy. This was due to the geographical position of the Duchy of Benevento in the Lombard Kingdom: it was far from Pavia, the king's capital city, and it was relatively isolated from other Lombard territories. Since a dynasty was established here as early as the seventh century, these dukes developed a strong and precocious political consciousness. As a result, they were particularly concerned with the formal representation of their authority, which is early attested in both coinage and diplomas. In this chapter, the analysis of the eight-century judicial records opens two important perspectives on the duke of Benevento's practices of power. Firstly, judicial assemblies were one of the most important occasions for the duke to demonstrate and exercise his authority in a public context. In contrast to all other Lombard dukes, who rendered judgement together with a group of officers, the duke of Benevento acted alone before the competing parties. By behaving exactly as the Lombard king would in Pavia, the duke was able to utilise the judicial domain as a sort of theatre in which to practice, legitimise and represent his own public authority in front of the local aristocracy. Secondly, the analysis of seven judicial case-studies suggests that the duke was not simply the sole political authority in Benevento but also the leading social agent in the whole Lombard southern Italy. Almost all the disputes transmitted by the twelfth-century cartularies implied a ducal action, donation or decision in the past, which became the main cause for later conflicts between the members of the lay élite and the monastic foundations of the region. Consequently, the analysis of judicial conflicts reveals more about the duke of Benevento's strategies and practices of power than about the lay and ecclesiastical élites' competition for power. Since there are no judicial records between 774 and the last decade of the ninth century, both conflicts and representations of authority in Lombard Southern Italy are analysed through other kinds of sources for this period. Chronicles, hagiographies, diplomas, and material sources are rich in clues about political and social competition in Benevento. By contrast, the late-ninth-century judicial records transmitted by cartularies and archives are quite different from the eighth-century documents: they have a bare and simple structure, which often hides the peculiarities of the single dispute by telling only the essentials of each conflict and a concise final judgement. In contrast to the sources of the ducal period, the ninth- and tenth-century judicial records often convey a flattened image of Lombard society. Their basic structure certainly prevents a focus on the representation of authority and the practices of power in southern Italy. On the contrary, these fields of inquiry are crucial to research both competition within the Beneventan aristocracy during the ninth century, and the relationship between Lombards and Carolingian after 774. After the fall of the Lombard Kingdom in 774, Charlemagne did not complete the military conquest of the Italian peninsula: the Duchy of Benevento was left under the control of Arechis (758-787), who proclaimed himself princeps gentis Langobardorum and continued to rule mostly independently. The confrontation and competition with the Frankish empire are key to understanding both the strengthening of Lombard identity in southern Italy and the formation of a princely political authority. The second account the historiography on the Regnum Italiae, the third section of this chapter focuses precisely on the ambitions of Louis II in Southern Italy and it analyses the implication that the projection of his rulership over this area had in shaping his imperial authority. Despite Louis II's efforts to control the Lombard principalities, his military and political experience soon revealed its limits. After the conquest of Bari in 871, Prince Adelchi imprisoned the emperor in his palace until he obtained a promise: Louis II swore not to return to Benevento anymore. Although the pope soon liberated the emperor from this oath, he never regained a political role in Southern Italy. Nevertheless, his prolonged presence in the region during the ninth century radically changed the political equilibrium of both the Lombard principalities and the Tyrrhenian duchies (i.e. Napoli, Gaeta, Amalfi). The fourth section focuses firstly on the competition between Louis II and Adelchi of Benevento, who obstinately defined his public authority in a direct competition with the Carolingian emperor. At the same time, the competition within the local aristocracy in Benevento radically changed into a small-scale struggle between the members of Adelchi's kingroup, the Radelchids. At the same time, some local officers expanded their power and acted more and more autonomously in their district, such as in Capua. When Louis II left Benevento in 871, both the Tyrrhenian duchies and the Lombard principalities in Southern Italy were profoundly affected by a sudden change in their mutual relations and even in their inner stability. The competition for power and authority in Salerno and Capua-Benevento also changed and two different political systems were gradually established in these principalities. Despite the radical transformation of internal competition and the Byzantine conquest of a large part of Puglia and Basilicata at the end of the ninth century, the Lombard principalities remained independent until the eleventh century, when Southern Italy was finally seized by Norman invaders.