Eleonora di Garzia di Toledo or Leonor Álvarez de Toledo Osorio, more often known as "Leonora" or "Dianora", was the daughter of García Álvarez de Toledo, 4th Marquis of Villafranca, Duke of Fernandina. Leonora was born in Florence, where she was brought up by Cosimo I de' Medici, Grand Duke of Tuscany and his wife Eleanor of Toledo, her aunt and namesake. Betrothed to their son Pietro at the age of 15, she blossomed under the wing of Pietro's older sister, the artistic patron Isabella, into a vivacious and witty beauty. Her marriage, like Isabella's, was not a success, and she followed her mentor's example of taking lovers. For this reason, Pietro had her brought in 1576 to the country retreat of Cafaggiolo, where he strangled her to death with a dog leash. Cosimo's successor, Francesco I, tacitly approved the murder, and Pietro was never brought to justice for it.

Cosimo I de' Medici was the second duke of Florence from 1537 until 1569, when he became the first grand duke of Tuscany, a title he held until his death.