She was the second daughter of Pedro Álvarez de Toledo, Viceroy of Naples, and Maria Osorio y Pimentel, 2nd Marquise of Villafranca del Bierzo.

On her paternal side, Eleanor was the third cousin of the Emperor since their great-grandmothers were daughters of Fadrique Enríquez de Mendoza, a great-grandson of King Alfonso XI of Castile.

Three years later, Cosimo, now Duke of Florence, was searching for a wife who could help strengthen his political position since the Medici were still new to their ducal status.

[4] He initially asked to marry Margaret of Austria, illegitimate daughter of Charles V and Alessandro's widow, but she displayed enormous reluctance at the idea to serve her father's own plans for her.

In May, Florencian agent Jacobo de' Medici was in Naples and informed the ducal secretary, Pierfrancesco Riccio, that "The Lady Duchess says she is happy and filled to the brim with satisfaction, and I want to assure of this."

[9] 29 June 1539 marked Eleanor and Cosimo's grandiose entrance from the Porta al Prato to the Church of San Lorenzo for their wedding in a grand, lavish celebration.

Their royal ancestors provided the Medici with the blue blood they had lacked and began the process of placing them on equal footing with other European sovereigns.

Her motto was cum pudore laeta fecunditas (meaning "happy fruitfulness with chastity"), making reference to the plentiful harvests of her lands, her marital fidelity, and numerous children.

So great was his trust in her political skills that in his frequent absences, the Duke made his wife regent, a station which established her position as more than just a pretty bearer of children.

She financially supported Cosimo's policies to restore the duchy's independence from foreign lands and helped people unable to gain audiences with the Duke realize that through the Duchess their causes could at least be pleaded.

In 1547, Juan Polanco, sent by Ignatius de Loyola to preach in Pistoia, approached the Duchess and asked for her patronage to founding a Jesuit college.

From 1559 to 1564, she commissioned Vasari to make a new fresco in her apartments about famous women whose actions, in his words, have equalled or surpassed men, such as Queen Esther, Penelope, and Florentine heroine Gualdrada.

It is thought that the redecorations were a concerted effort on the middle age Eleanor's part to reshape her public persona away from fecundity and towards other her virtues – wisdom, valour, and prudence.

In 1550, she commissioned and supervised Tribolo to create the Pitti's famous Boboli Gardens, which possess an openness and expansive view unconventional for its time.

[16] It was built around the Sale del Papa of the prominent Dominican monastery Santa Maria Novella, which once functioned as quarters for visiting popes.

[17] In 1544, Eleanora adeptly instructed Andrea Pasquali, the court physician, to formulate and administer a salve made out of distilled human fat to her daughter Maria after she received a gash on her head while playing.

How medicine was employed at the court reinforced a ranking system marked by status, but Eleanora also extended access to healthcare for many relatives, visitors, and courtiers.

The early Medici court held an account at the Canto del Giglio apothecary for the benefit of its courtiers,[20] which helped secure future political support.

Similar to her mother-in-law, Eleanora demonstrated proficient pharmaceutical ability and knowledge, as a number of correspondences indicate her proclivity for ordering or instructing the creation of medicinal remedies and recipes.

All perfumes at this time were meant to protect and strengthen the brain from malignant humors, but this one was also good for the heart because it contained myrtle and neroli in its composition.

[22] Though Eleanor was sick for much of her adult life, suffering from a "chronic cough" and recurring fever, she was considered very charming, loved to gamble[23] and was a devoted traveler, moving endlessly throughout her palazzi and villas.

Although she didn't support the Spaniards gaining control of Florence, Eleanor showed pride in her birthplace and preferred to write in Spanish than Italian, which would sometimes cause communication problems in letters with her husband.

The rebuilding of the Pitti Palace was only partially completed at the time of Eleanor's death, but eventually became the principal residence of the grand rulers of Tuscany.