Isabella of Portugal

Engagement and marriage

Isabella, eldest daughter of Manuel the Fortunate, was considered a strong candidate for marriage to her first cousin Charles, son of Joanna I of Castile and Philip, Duke of Burgundy. Such a union would align with the wishes of their grandparents, Isabella I of Castille and Ferdinand II of Aragón, and prevent Portugal from falling under French influence, as had occurred in the War of Castilian Succession. Spanish nobles insisted Charles marry an Iberian princess, but the 18-year-old Charles was in no hurry and instead sent his sister Eleanor to wed Isabella's widowed father in 1518.

Many in Portugal viewed this rejection as an offense, but Isabella remained determined to marry her cousin or enter a convent. By 1525, Charles abandoned the English alliance, ended the engagement, and sought to marry Isabella. She was closer to his age, fluent in Spanish, and offered a dowry of 900,000 Portuguese cruzados, which helped alleviate financial strains from the Italian War of 1521–26.

Regency

Charles appointed Isabella regent of Spain during his absences from the peninsula between 1529–33 and 1537–39. She attended governing council meetings, consulted ministers, and gradually took an active role in policymaking, proposing her own solutions. She maintained regular correspondence with Charles, informing him of political, military, and financial developments while receiving instructions on imperial affairs. As regent, she presided over royal councils, signed decrees in the king's name, supervised appointments, and oversaw administration of the Indies.

She appointed Diego López de Medrano as her mayordomo mayor to organize the royal household. Her government coordinated defence of the Mediterranean and Atlantic coasts against Barbary corsair raids while supporting Charles's campaigns in Italy and North Africa. Her prudent fiscal administration helped preserve Castile's relative prosperity during her regencies, though after her death the kingdom faced mounting inflation and fiscal difficulties. She traveled regularly between Toledo, Valladolid, Seville, Barcelona, and Majorca, and intervened in negotiations of marital alliances between French and Spanish royal families, concerned her children would not be forced to wed older offspring of King Francis I.

Death

Isabella and the court moved frequently to avoid epidemics. She was described as extremely thin, and speculation arose that she suffered from consumption. In 1539, she became pregnant for the seventh time but contracted a fever in the third month, leading to antenatal complications and the birth of a stillborn son. She died two weeks later on 1 May 1539 at age 35, without her husband present.

Charles was so devastated he could not accompany her body to the Royal Chapel of Granada; their son Philip accompanied it instead, with Francis Borgia, 4th Duke of Gandía. Decomposition had so disfigured Isabella's body that Gandía could not recognize her, and he was allegedly so horrified that he later became a Jesuit. Charles shut himself in a monastery for two months, praying and mourning in solitude, wore black for the rest of his life, and never remarried. He died as a widower in 1558 holding the same cross she held when she died.

Post-mortem tributes

In 1540, Charles commissioned Flemish composer Thomas Crecquillon to compose new music in honour of the empress, resulting in Missa Mort m'a privé, which expressed grief and a wish for heavenly reunion. Another musical tribute, Carole cur defles Isabellam, was composed in 1545 by Nicolas Payen. In 1543, Charles commissioned Titian to paint posthumous portraits of Isabella using earlier models; Titian produced several works including Portrait of Isabella of Portugal and La Gloria, and later a double portrait of the imperial couple. Charles kept these portraits with him during travels and after retiring to the Monastery of Yuste in 1555.

Did You Know?

• Isabella was second-in-line to the Portuguese throne until the birth of her brother Luis in 1506.
• Her education included mathematics, Renaissance classics, Latin, Spanish, French, etiquette, and Christian doctrine.
• At age 14, her mother died, and Isabella and her sister Beatrice inherited her properties plus income from Viseu and Torres Vedras.