Desiderius, the last king of the Lombards, is chiefly known through his connection with Charlemagne.

He was duke of Tuscany and became king of the Lombards after the death of Aistulf in 756. Seeking, like his predecessors, to extend the Lombard power in Italy, he came into collision with the papacy, and about 772 the new pope, Adrian I, implored the aid of Charlemagne against him.

Other causes of quarrel already existed between the Frankish and the Lombard kings. In 770 Charlemagne had married a daughter of Desiderius, but he soon divorced her and sent her back to her father. Moreover, Gerberga, the widow of Charlemagne's brother Carloman, had sought the protection of the Lombard king after her husband's death in 771; and (probably in return for the slight cast upon his daughter) Desiderius had recognized Gerberga's sons as lawful Frankish kings, and had attacked Adrian for refusing to crown them.

Such was the position when Charlemagne led his troops across the Alps in 773, took the Lombard capital, Ticinum, the modern Pavia, in June 774, and added the kingdom of Lombardy to his own dominions. Desiderius was exiled to France, where he died, and his son, Adalgis , spent his life in futile attempts to recover his father’s kingdom. The name of Desiderius appears in the romances of the Carolingian period. Charlemagne took the title King of the Lombards, the first time one of the Germanic kings adopted the title of a kingdom he had conquered.