Joanna (Spanish: Juana) (November 6, 1479 – April 11, 1555), called the Mad (la Loca), queen of Castile and mother of the Holy Roman Emperor Charles V, was the second daughter of Ferdinand and Isabella, king and queen of Spain, and was born at Toledo on November 6, 1479.

Her youngest sister was Catherine of Aragon, the first wife of Henry VIII. In 1496 at Lille, Joanna was married to the archduke Philip the Handsome, son of the German King Maximilian I, and at Ghent in February 1500, she gave birth to the future emperor.

The death of her only brother John, of her eldest sister Queen Isabella, queen of Portugal, and then of the latter's infant son Miguel, made Joanna the heiress of the Spanish kingdoms, and in 1502 the cortes of Castile and of Aragon recognized her and her husband as their future sovereigns.

Soon after this, Joanna's reason began to give way. She mourned in an extravagant fashion for her absent husband, whom at length she joined in Flanders; in this country her passionate jealousy, although justified by Philip's conduct, led to deplorable scenes. In November 1504 her mother's death left Joanna queen of Castile, but as she was obviously incapable of ruling, the duties of government were undertaken by her father, and then, for a short time, by her husband.

The queen was with Philip when he was wrecked on the English coast and became the guest of Henry VII at Windsor; soon after this event, in September 1506, he died, and Joanna became completely deranged -- it was almost impossible to get her away from the corpse of her husband. The remaining years of her miserable existence were spent at Tordesillas , where she died on April 12, 1555.

In spite of her afflictions, the queen was sought in marriage by Henry VII just before his death. Nominally, Joanna remained queen of Castile until her death, her name being joined with that of Charles in all public documents, but of necessity she took no part in the business of state.

She had six children:

• Eleanor (1498-1558), Queen consort first to Manuel I of Portugal and secondly to Francis I of France.
• Charles V, Holy Roman Emperor, King of Spain (1500-1558).
• Isabella of Burgundy (1501-1525), Queen consort of Christian II of Denmark.
• Ferdinand I, Holy Roman Emperor (1503-1564).
• Maria of Austria (1505-1558), Queen consort of Louis II of Hungary and Bohemia.
• Catherine of Habsburg (1507-1578), Queen consort of John III of Portugal.

Biographies :

• W. H. Prescott, Hist. of Ferdinand and Isabella (1854)
• Rosier, Johanna die Wahnsinnige (Vienna, 1890)
• H. Tighe, A Queen of Unrest (1907).
• R. Villa, La Reina doña Juana la Loca (Madrid, 1892)