Pietro Tradonico (Latin: Petrus Tradonicus) (died 13 September 864), an Istrian by birth, was the Doge of Venice from 836 to 864. He was, according to tradition, the thirteenth doge, though historically he is only the eleventh. His election broke the power of the Participazio.
He was illiterate, and forced to sign all state documents with the signum manus. He was a warrior, not an administrator.
He nominated his son Giovanni as co-doge, continuing the process begun a century earlier of establishing a hereditary dukedom and dynastic succession. All previous attempts had failed and this was no different: Giovanni predeceased his father.
He fought the Saracens of Bari and Taranto, who had earlier defeated Venice in the Battle of Sansego, on an island south of Pola. He had to deal not only with Saracen pirates, but with Slavs as well. He led a large fleet against in 839 to punish the Narentines for raiding and slaughtering several Venetian traders returning from Benevento in 834–835. He made peace with Duke Mislav of the Croats of Dalmatia and a Narentine prince by the name of Družak (Drosaico, Marianorum judice). His military assault on the Neretvians in 840 failed and he lost more than 100 men and had to return Venetia. The Neretvians continued to push against him and, in 846, breached Venice itself and raided the neighbouring lagoon city of Caorle.
In 840, the Emperor Lothair I recognised the independence of Venice and its authority over the lagoon as far as acquas salsas, already recognised by Byzantium. From the latter he received the titles of spatharius and hypatus.