Biography of Queen Isabella I of Castile

The Co-Ruler of Castile and Aragon

Portrait of Queen Isabella I of Castile
Queen Isabella I of Castile, c. 1490. Found in the collection of the Museo del Prado, Madrid.

Fine Art Images/Heritage Images/Getty Images 

Isabella I of Spain was Queen of Castile and León in her own right, and through marriage, Queen of Aragon. She married Ferdinand II of Aragon, bringing the kingdoms together in what became Spain under the rule of her grandson, Charles V, Holy Roman Emperor. She is known for sponsoring Columbus' voyage to the Americas. She was known as Isabel la Catolica or Isabella the Catholic for her role in "purifying" the Roman Catholic faith through expelling Jews and defeating the Moors. 


At her birth on April 22, 1451, Isabella was second in line of succession to her father, with an older half-brother, Henry. She became third in line when her younger brother Alfonso was born in 1453. Her mother was Isabella of Portugal, whose father was a son of John I of Portugal and whose mother was a granddaughter of that same king. Her father was King John (Juan) II of Castile (1405 - 1454) of the house of Trastámara. His father was Henry III of Castile, and his mother was Catherine of Lancaster, the daughter of John of Gaunt (third son of England's Edward III) and John's second wife, the Infanta Constance of Castile (1354 - 1394) of the house of Burgundy.

Power Politics

Isabella's half-brother, Henry IV, became king of Castile when their father, John II, died in 1454. Isabella was only three years old, and her younger brother Alfonso was the next in line to the Castilian throne after Henry. Isabella was raised by her mother until 1457 when the two children were brought to court by Henry IV to keep them from being used by opposition nobles.

Beatriz Galindo

Isabella was well-educated. Her tutors included Beatriz Galindo, a professor at the University at Salamanca in philosophy, rhetoric, and medicine. Galindo wrote in Latin, producing poetry and commentary on Aristotle and other classical figures.

Succession Struggles

Henry's first marriage ended without children and in a divorce. When his second wife, Joan of Portugal, bore a daughter, Juana, in 1462, the opposition nobles soon claimed that Juana was the daughter of Beltran de la Cueva, Duke of Albuquerque. Thus, she's known in history as Juana la Beltraneja.

The opposition's attempt to replace Henry with Alfonso met with defeat, the final defeat coming in July 1468 when Alfonso died of suspected poisoning, though historians consider it more likely he died of the plague. He had named Isabella his successor. Isabella was offered the crown by the nobles, but she refused, probably because she did not believe that she could maintain that claim in opposition to Henry. Henry was willing to compromise with the nobles and accept Isabella as his heiress in September.

Marriage to Ferdinand

Isabella married Ferdinand of Aragon (a second cousin) in October 1469 without Henry's approval. The cardinal of Valentia, Rodrigo Borgia (later Pope Alexander VI), helped Isabel and Ferdinand obtain the necessary papal dispensation, but the couple still had to resort to pretenses and disguise to carry out the ceremony in Valladolid.  Henry withdrew his recognition and again named Juana as his heir. At Henry's death in 1474, a war of succession ensued, with Alfonso V of Portugal, prospective husband of Isabella's rival Juana, supporting Juana's claims. The war was settled in 1479, with Isabella recognized as Queen of Castile. Juana retired to a convent rather than marry the son of Ferdinand and Isabella, Juan. Juana died in 1530.

Ferdinand had by this time become King of Aragon, and the two ruled with equal authority in both realms, thus unifying Spain. Among their first acts were various reforms to reduce the power of the nobility and increase the power of the crown.

After her marriage, Isabella appointed Beatrix Galindo as tutor to her daughters. Galindo founded hospitals and schools in Spain, including the Hospital of the Holy Cross in Madrid. She probably served as an advisor to Isabella after she was queen.

The Catholic Monarchs

In 1480, Isabella and Ferdinand instituted the Inquisition in Spain, one of many changes to the role of the church instituted by the monarchs. The Inquisition was aimed mostly at Jews and Muslims who had overtly converted to Christianity but were thought to be practicing their faiths secretly, known respectively as morranos and moriscos, as well as heretics who rejected Roman Catholic orthodoxy, including alumbras who practiced a kind of mysticism or spiritualism.

Ferdinand and Isabella were given the title "the Catholic monarchs" (los Reyes Católicos) by Pope Alexander VI, in recognition of their role in "purifying" the faith. Among Isabella's other religious interests, she also took a special interest in the order of nuns, the Poor Clares.

Isabella and Ferdinand proceeded with their plans to unify all of Spain by continuing a long-standing but stalled effort to expel the Moors (Muslims) who held parts of Spain. In 1492, the Muslim Kingdom of Granada fell to Isabella and Ferdinand, thus completing the Reconquista. That same year, Isabella and Ferdinand issued a royal edict expelling all Jews in Spain who refused to convert to Christianity.

Christopher Columbus and the New World

Also in 1492, Christopher Columbus convinced Isabella to sponsor his voyage of exploration. The lasting effects of this were many: by the traditions of the time, when Columbus was the first European to encounter lands in the New World, the lands were given to Castile. Isabella took a special interest in the Native Americans of the new lands; when some were brought back to Spain as slaves she insisted they be returned and freed, and her will expressed her wish that the "Indians" be treated with justice and fairness.

Art and Education

Isabella was also a patron of scholars and artists, establishing educational institutions and building a large collection of artworks. She learned Latin as an adult, was widely read, and educated not only her sons but her daughters. The youngest of these daughters, Catherine of Aragon, is known in history as the first wife of Henry VIII of England and mother of Mary I of England.


At her death on November 26, 1504, Isabella's sons and grandsons and her older daughter Isabella, queen of Portugal, had already died. That left as Isabella's only heir "Mad Joan," Juana.

Isabella's will, the only writing which she left, is a fascinating document, summarizing what she thought were her reign's achievements as well as wishes for the future.

In 1958, the Roman Catholic church began the process to canonize Isabella. After a long and exhaustive investigation, the commission that was appointed determined that she had a "reputation of sanctity" and was inspired by Christian values. In 1974 she was recognized with the title "Servant of God" by the Vatican.

Children of Isabella and Ferdinand

  1. Isabella (1470 - 1498), married first Alfonso, a Portuguese prince, then Manuel I of Portugal.
  2. Stillborn Son (1475)
  3. John (Juan) (1478 - 1497), Prince of Asturias, married Margaret of Austria.
  4. Her heir, Juana (Joan or Joanna), known as "The Mad" or "La Loca" (1479 - 1555), married Philip I, bringing Spain into the Habsburg sphere.
  5. Maria (1482 - 1517), married Manuel I of Portugal after the death of his first wife, Maria's older sister Isabella.
  6. Maria's twin, stillborn (1482)
  7. Catherine of Aragon (1485 - 1536), first wife of Henry VIII of England.

The descendants of Isabella's daughters, Juana, Catherine, and Maria, often intermarried.