Lucius Calpurnius Piso Caesoninus, statesman of ancient Rome, was the father-in-law of Julius Caesar.
In 58 BC, when consul, he and his colleague Aulus Gabinius entered into a compact with P. Clodius, with the object of getting Cicero out of the way. Piso's reward was the province of Macedonia, which he administered from 57 to the beginning of 55, when he was recalled, perhaps in consequence of the violent attack made upon him by Cicero in the senate in his speech De provinciis consularibus.
On his return Piso addressed the senate in his defence, and Cicero replied with the coarse and exaggerated invective known as In Pisonem. Piso issued a pamphlet by way of rejoinder, and there the matter dropped, Cicero being afraid to bring the father-in-law of Caesar to trial. At the outbreak of the civil war Piso offered his services as mediator, but when Caesar marched upon Rome he left the city by way of protest. He did not, however, definitely declare for Pompey, but remained neutral, without forfeiting the respect of Caesar.
After the murder of the dictator he insisted on the provisions of his will being strictly carried out, and for a time opposed Antony. Subsequently, however, he became one of his supporters, and is mentioned as taking part in an embassy to Antony's camp at Mutina with the object of bringing about a reconciliation.
He is believed to have been the owner of the 'Villa of the Papyri' at Herculaneum.
