Agostino Andrea Chigi (29 November 1466 – April 11, 1520) was an Italian banker and patron of the Renaissance.

Born in Siena, he was the son of the prominent banker Mariano Chigi, a member of an ancient and illustrious house. He moved to Rome around 1487, collaborating with his father. The heir of a rich fund of capital, and enriched further after lending huge amounts of money to Pope Alexander VI (and to other rulers of the time as well), he strayed from common mercantile practice by obtaining lucrative monopolies like the salt monopoly of the Papal States and the Kingdom of Naples, as well as that of the alum excavated in Tolfa, Agnato and Ischia di Castro. Alum was an essential mordant in the textile industry.

After the death of the Borgia pope Alexander VI and his short-lived Sienese successor Pius III Piccolomini, he helped Pope Julius II in the expenses attendant upon his election. The latter rewarded him, linking Chigi to the della Rovere family, and creating him treasurer and notary of the Apostolic Camera. The personal bond between the Pope and his banker remained close: Agostino accompanied Julius in the field in both his great military campaigns of 1506 and 1510. In 1511 Agostino was sent to Venice to buy Venetian support for the papal forces in the War of the League of Cambrai.