a Sienese family that rose from banking in the 13th century to princely rank in papal Rome and in the Holy Roman Empire in the 17th century.

The first member of the family to win more than local eminence was Agostino Chigi, “il Magnifico” (c. 1465–1520), a merchant prince who, as a banker in Rome, developed one of the richest business houses in Europe, lending money to popes, administering church revenue, and spending lavishly on display and the patronage of artists and writers. It was he who built the palace and gardens later known as the Farnesina, decorated by Raphael.

Another member of the family who contributed much to its rise to prominence was Fabio Chigi, who was elected pope as Alexander VII in 1655. As pope he created his nephew Agostino (distinct from “il Magnifico”) successively Prince of Farnese (1658), Prince of Campagnano (1661), and Duke of Ariccia (1662); the Holy Roman emperor Leopold I also made Agostino a prince of the empire (1659). After Alexander's death this Roman branch of the Chigi family continued to prosper in the service of the papacy. In 1852, on the extinction of the Albani family, with whom they had intermarried in 1735, they added that name to their own, becoming known as the Chigi-Albani.

As cardinal and then as pope, Fabio Chigi was mainly responsible for gathering the Biblioteca Chigiana, a rich collection of manuscripts and books, now incorporated in the Vatican Library.