Gnaeus Calpurnius Piso (ca. 44 BC/43 BC - 20 AD), Roman statesman, was consul in 7 BC; subsequently, he was governor of Hispania and proconsul of Africa.
In AD 17 Tiberius appointed him governor of Syria (with an army of 4 legions). Some Roman sources of the period suggest that Tiberius gave Piso secret instructions to thwart and control Germanicus, who had been sent to supervise all Eastern provinces. Piso and Germanicus clashed on several occasions and, in AD 19, Piso had to leave the province. At the death of Germanicus during the same year most people suspected Piso of having poisoned him (although no definite proof was available).
The armed attempt of Piso to gain once more control of the province of Syria immediately after the death of Germanicus only aroused more indignation, and Tiberius was forced to order an investigation and a public trial in the Roman Senate for Piso and his wife. Piso committed suicide, though it was rumoured that Tiberius, fearing incriminating disclosures, had put him to death. Tiberius and his mother Livia were able to avoid incrimination of his wife Plancina.