Eleonora di Garzia di Toledo or Leonor Álvarez de Toledo Osorio (March 1553 – 10 July 1576), 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 raised 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 was mentored by Pietro's older sister, the artistic patron Isabella de' Medici, and was considered 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 punished for it.
Until recently, little was known of Leonora di Garzia di Toledo, and she was not identified as the sitter of several portraits of her. The facts of her life have emerged from the growing scholarship on Isabella de' Medici, with whom she has much in common. In the view of art historian Gabrielle Langdon, "Her story is valuable in revealing attitudes and legalities attendant on the lives and decorum of women in the early-modern Italian court".
Born at the Florentine court in March 1553, Leonora was the daughter of García Álvarez de Toledo y Osorio, Marquis of Villafranca del Bierzo and Duke of Fernandina, and Vittoria d'Ascanio Colonna. Her father and mother were staying in Florence because García Álvarez had charge of the castles of Valdichiana in the region. When Vittoria Colonna died a few months later, Leonora was left in the care of her aunt Eleonora, the Grand Duchess of Florence. Eleonora and Cosimo raised her lovingly at the Medici court, where she remained for the rest of her life, in effect a menina—a girl groomed for a life at court, in the Spanish tradition of courtly fostering.
García Álvarez went on to become the Viceroy of Catalonia (1558–64) and the Viceroy of Sicily (1564–66) on behalf of Philip II of Spain, and served as Philip's commander at the Battle of Lepanto in 1571. He was the son of Pedro Álvarez de Toledo (1484–1553), the Spanish Viceroy of Naples. The family came from the grandee class of Spanish nobles, the highest in the land, which was often entrusted with viceroyal powers in Spanish and Habsburg territories; Toledo has been called "Christendom's wealthiest benefice". In 1539, Pedro Alvarez de Toledo's daughter Eleonora had been married to the Grand Duke of Florence, Cosimo I de' Medici, as part of a process of legitimising the Medici grand ducal title, granted only in 1532, under Habsburg auspices. She went on to bear Cosimo 11 children, including the future grand dukes Francesco and Ferdinando, as well as Pietro and Isabella.
After Eleonora died in 1562, Cosimo's daughter Isabella replaced her as the first lady of Florence. She acted as a surrogate consort and also took over the supervision of Leonora's upbringing. The red-headed Leonora, who possessed a natural charm, was popular in the Medici family. At the age of five, she was reported as being a comfort to Cosimo's second daughter Lucrezia, from whom she became inseparable, when Lucrezia was apart from her husband Alfonso d'Este. Lucrezia died in 1561, leaving Isabella as Cosimo's only surviving daughter; the grand duke was, however, extremely fond of Leonora, and treated her as his own daughter. He was charmed by her vivacity and physical vigour—she delighted in horsemanship and arms—though he occasionally gently reminded her to behave with more decorum. Owing to the close family and political ties between the House of Medici and the viceroyal family of Toledo, a marriage was arranged between Leonora and Cosimo's son Pietro, with whom she had grown up and who was of a similar age. The couple were betrothed in 1568 when Leonora was 15, with the approval of Philip II of Spain. Garcia Álvarez de Toledo provided her with a dowry of 40,000 gold ducats. They were married at the Palazzo Vecchio in April 1571, and it was reported that Pietro had to be forced to consummate the union. On 10 February 1573, Leonora gave birth to a son, Cosimo ("Cosimino"), who was the sole male Medici heir in this generation until his death three years later, in August 1576, one month after his mother's death. According to rumors, the infant was poisoned on the orders of Pietro, who doubted his paternity.
For Leonora, the marriage brought both advantages and disadvantages. On the one hand, it cemented her relationship with one of the richest families in Europe and allowed her to remain at a court where women were often granted more freedom, or at least discretion, than elsewhere; on the other hand, Pietro was the least stable of the Medici offspring, exhibiting from an early age a cruel and disturbed temperament that troubled his parents. As a result, the marriage, unlike that of Cosimo and Eleonora, was never a physical and emotional success. In this it resembled that of Isabella de' Medici, whose protégée Leonora became, and Paolo Giordano I Orsini. Duke Cosimo had married his beloved daughter Isabella into the House of Orsini for political reasons, to strengthen his position on the borders of southern Tuscany. Although Isabella had two children by Paolo Giordano, she had chosen not to live at her husband's castle at Bracciano or in Rome, where he conducted his political and amorous affairs. Instead, with Cosimo's permission, she had remained in Florence, cultivating an artistic salon at her Villa Baroncelli in the south of the city, and discreetly taking lovers, notably Troilo Orsini, a cousin of her husband's. Leonora became part of Isabella's circle and renowned for her beauty and vivacity. Like Isabella, she sponsored charities and the arts, serving as the patron of the literary Accademia degli Alterati. Neglected by her husband, she also followed Isabella's example in taking lovers. Under the liberal Cosimo, such behaviour was tolerated as long as discretion was maintained and the marriages reaped political advantages. The women's respective husbands conducted affairs of their own, leading largely separate lives.
Thus matters stood until the death of Cosimo, by then raised to the title of grand duke, in 1574. His son and successor, the reclusive Grand Duke Francesco, was, however, very different. Though he maintained a mistress of his own, much to the distress of his wife, Joanna of Austria, Cosimo's eldest son was a much less sociable and tolerant ruler than his father. Rather than attend court and participate in the artistic life of Florence, he preferred to pursue science, often locking himself up in his laboratory in the Casino of San Marco to carry out experiments in alchemy, poisons, and porcelain-making. Unfortunately for Isabella, her brother did not look upon her lifestyle as indulgently as their father Cosimo. While he continued to cultivate the advantageous relations between her husband's house and Florence, he was less willing to turn a blind eye to the behaviour of Isabella and Leonora and to the complaints of their spouses, for whom their adultery was a question of honour rather than jealousy. Eleven years younger than Isabella, Leonora was somewhat less prudent in her amorous adventures. Neither woman, however, grasped the danger posed to them by the new regime or the extremity of the plotting that began to coil against them.
On 11 July 1576, Pietro de' Medici sent a note to his brother, Grand Duke Francesco, from the Villa Medici at Cafaggiolo, north of Florence: "Last night at six hours an accident occurred to my wife and she died. Therefore Your Highness be at peace and write me what I should do, and if I should come back or not." The next day, Francesco wrote to his brother Ferdinando in Rome: "Last night, around five o'clock, a really terrible accident happened to Donna Leonora. She was found in bed, suffocated, and Don Pietro and the others were not in time to revive her".