Born in Florence, son of Piero Ridolfi and Contessina de' Medici (the daughter of Lorenzo de' Medici the Magnificent), he was therefore nephew of Pope Leo X, who granted him a quick ecclesiastical career. He was named governor of Spoleto in the period 1514-1516 and protonotary apostolic at the age of thirteen. After the death of Pope Paul III he was a papabile, entered the conclave of 1549 - 1550, but left because of illness. He died on January 31, 1550 of an apoplexy before the new Pope Julius III was elected on February 7, 1550. Cardinal Ridolfi was buried in the church of Sant'Agostino.