Piso (pī`sō), distinguished family of the ancient Roman gens Calpurnia. One of the best-known members was Lucius Calpurnius Piso Caesoninus, d. after 43 B.C., father-in-law of Julius Caesar. As consul (58 B.C.), he aided in the banishment of Cicero; Macedonia was his proconsular province (57 B.C.–55 B.C.). Cicero, after he returned from exile in 57 B.C., attacked him in the senate for extortion, especially in the orations De provinciis consularibus and In Pisonem. In 50 B.C., Piso was censor. Caius Calpurnius Piso, d. A.D. 65, was a prominent patron of literature. He led a conspiracy against Nero; it was discovered, and Piso killed himself.