Lucius Calpurnius Piso Caesoninus (consul 58 BC)

Lucius Calpurnius Piso Caesoninus (c. 100 BC – 43 BC) was a Roman and the father-in-law of Julius Caesar through his daughter Calpurnia. He also had a son, Lucius Calpurnius Piso, known as "the Pontifex", who was Consul in 15 BC. He was reportedly a follower of a school of Epicureanism that had been modified to befit politicians, as Epicureanism itself favored withdrawal from politics.

In 58 BC, when consul, Piso and his colleague, Aulus Gabinius, entered into a compact with Publius Clodius, with the object of getting Marcus Tullius Cicero out of the way. Piso's reward was the province of Macedonia, which he administered from 57 BC to the beginning of 55 BC, when he was recalled and the province was given to Quintus Ancharius. Piso's recall was perhaps in consequence of the violent attack made upon him by Cicero in the Senate in his speech "De provinciis consularibus".

Caesar mentions his father-in-law in his Gallic Commentaries. Piso's grandfather, also named L. Calpurnius Piso, was killed by the same Gauls that Caesar would later conquer.

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 ended. Cicero may have been afraid to bring the father-in-law of Julius Caesar to trial. At the outbreak of the civil war, Piso offered his services as mediator. However, when Caesar marched upon Rome, he left the city by way of protest of Caesar. Piso did not openly declare support for Gnaeus Pompeius Magnus and remained neutral but is widely believed he secretly supported Pompey but still did not forfeit the respect of Caesar when Pompey was defeated.

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