Bianca Capello, grand duchess of Tuscany, born in Venice in 1542, died at Poggio, Oct. 19, 1587. In 1563 she eloped with a banker's clerk named Pietro Buonaventuri, who put himself under the protection of Francesco de' Medici at Florence. Bianca's beauty and accomplishments fascinated Francesco, and although but recently married to Joanna, archduchess of Austria, he caused the Venetian woman to reside in his palace, attaching her husband to his household as steward. In 1570 Buonaven-turi was put to death by order of Francesco, who, on the decease of his father Cosmo I., had ascended the throne of Tuscany. Bianca presented him with a son Aug. 29, 1576, who however was not her own; and in order to pre-elude the detection of the imposture, she caused the assassination of most of those who had assisted her in its perpetration. In 1577 Joanna of Austria bore a son to the grand duke, and as she soon afterward died Bianca persuaded Francesco to make her his wife. The marriage was approved of by Philip II. of Spain, and ratified by the republic of Venice, the official marriage ceremony taking place in October, 1579. In 1582 Francesco's son by Joanna of Austria died, and Bianca endeavored to reconcile herself with Francesco's brother, the cardinal Fernando de' Medici, who in all probability would succeed him as grand duke.

In October, 1587, the two brothers and Bianca met at Poggio, and a few days afterward the grand duke and Bianca were taken suddenly ill, and both died. Bianca had ever been an object of hatred to her brother-in-law, and it was believed that Fernando had poisoned her with her husband ; but there is no evidence to prove it.