The Duchy of Sorrento is a small peninsular principality of the Early Middle Ages centered on the Italian city of Sorrento.Originally, Sorrento was part of the Byzantine Duchy of Naples in the Dark Ages, but in the ninth century, along with Amalfi and Gaeta, it breaks away from the Neapolitans to found its own ducatus (or republic).

However, it mostly remains under Amalfi and only one independent duke is known from this period, a Sergius in the late ninth century.In 1035, it is conquered by the Lombards under Guaimar IV of Salerno and bestowed on his younger brother Guy, who rules it until the 1070s.

Not long after that, it wis annexed by the Normans.In 1119, a certain Sergius undersigns a diploma of William II, Duke of Apulia, as "Prince of Sorrento."