Bianca Cappello (1548 – 20 October 1587) was an Italian noblewoman who was the mistress, and afterward the second wife, of Francesco I de' Medici, Grand Duke of Tuscany. Her husband officially made her his consort.

She was born in Venice, in 1548, the daughter of Bartolomeo Cappello and Pellegrina Morosini, a member of one of the richest and noblest Venetian families, and was noted for her great beauty.

At the age of fifteen she fell in love with Pietro Bonaventuri, a young Florentine clerk in the firm of Salviati, and on 28 November 1563 escaped with him to Florence, where they were married. In 1564 she had a daughter named Virginia, or, according to other sources, Pellegrina. The Venetian government made every effort to have Bianca arrested and brought back but the Grand Duke Cosimo I intervened in her favour and she was left unmolested.

However, she did not get on well with her husband's family, who were very poor and made her do menial work, until at last her beauty attracted Grand Prince Francesco, son and heir apparent of the grand duke.

Although already married to Joanna of Austria, Francesco seduced Bianca and gave her jewels, money and other presents. Bonaventuri, Bianca's husband, was given court employment and consoled himself with other ladies until, in 1572, he was murdered in the streets of Florence in consequence of some amorous intrigue. It is possible that Bianca and Francesco were involved.

On the death of Cosimo in 1574 Francesco succeeded to the grand duchy; he now installed Bianca in a palace (now known as Palazzo di Bianca Cappello) close to his own and outraged his wife by flaunting his mistress before her. At this point, Francesco had no legitimate son to inherit the duchy; a child by Bianca, though illegitimate, would be a potential heir, and by extension would secure Bianca's own position. In 1576 she duly gave birth to Don Antonio de' Medici (d. 1621), but his father, still hoping to have a legitimate son by his wife, refused to acknowledge him. Francesco and Joanna then produced a son, Grand Prince Philip de' Medici, in 1577; the child survived the perilous months of early infancy, and Bianca's hopes of being anything more than a favoured mistress seemed dashed.

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