Queen Isabella I Biography

Isabel_la_Catolica-2 Queen Isabella I of Castile (14511504) was an influential monarch who helped to unite the different regions of Spain and make Spain a leading power in Europe and the Americas. Queen Isabella was a strict Catholic and, amongst contemporaries, was noted for her ‘virtue and fear of God’. She was an effective monarch in bringing greater law and order to the country and had areputation for promoting justice rather than mercy. With her husband King Ferdinand, she set up the Spanish Inquisition, to investigate heretical religious practises.

Early life


Prince Ferdinand and Isabella

Isabella was born in 1451 in Madrigal in the Kingdom of Castile (part of Spain). Her half-brother Henry IV was King of Castile, and he wished Isabella to marry the King of Portugal in a marriage of convenience. Henry IV planned to make Isabella his successor. However, Isabella disliked her half-brother, and at the age of 18 in 1469 she married Prince Ferdinand – the heir to the Kingdom of Aragon – a neighbouring kingdom in Spain. As a result, Henry IV disinherited his half-sister in favour of his own daughter Juana.

Isabel_I_of_Castile In 1474, Henry IV died, and this led to conflict between supporters of Isabella and Juana for the throne of Castile. Initially, Isabella had only a few supporters amongst the powerful of Castille, but in December 1474, she had the confidence to have herself crowned as queen, usurping the former king’s daughter. It led to several years of conflict between the rival factions for the throne – during this period she showed her strength and resolve to cement her power. For example, in 1476, a rebellion broke out in Segovia. With her husband away, Isabella ignored her male advisers and took it upon herself to ride out to meet the rebels. She successfully negotiated with them to drop their grievances, and she was successful in bringing it to an end without bloodshed. At the time, it was unusual for women to take such an active approach to matters of the state. She was a pioneer for powerful and influential queens who would follow in the next few centuries.

In 1474 – her husband Ferdinand became King of Aragon. They agreed to rule together – becoming an effective couple who would discuss decisions and actions. Their joint rule led to increased centralisation and effective unification of the Spanish kingdoms. In 1479, she completed her triumph in securing the throne of Castile becoming undisputed queen. During her reign, she also oversaw a change in medieval warfare – because she vastly increased the numbers of cannon and this made castles much more vulnerable to attack. This had a big influence on the nature of warfare.

When Isabella came to the throne, the kingdom of Castille suffered serious problems due to misrule by her brother Henry IV. In particular, he had been profligate in spending and ignored issues of law and order. When Isabella came to the throne, there was no reliable system for bringing criminals to justice. She successfully financed a justice system and police force through a new tax. She was also successful in improving the nation’s finances by making better use of Royal lands, which has been sold cheaply by her brother. She also instituted a Royal monopoly over the money supply and this helped to increase confidence in the nation’s coins and finances.


One objective of Isabella and Ferdinand was to complete the ‘Reconquista’ of parts of Spain still under Muslim Rule. During her time, the last remaining objective was to claim the Kingdom of Grenada, which was still under the rule of the Moors (Muslims). After nine years of conflict, the armies of Isabella and Ferdinand defeated the Moors in 1492, and Grenada came into their orbit of power. It also marked the end of Islam in Spain. Despite signing a peace treaty which gave Moslems the right to practise their religion, the religious fervour of Isabella and Ferdinand caused this to be later revoked and Muslims were forced to convert or leave the country.

The Spanish Inquisition

Early in their reign, in 1478, they formed the Inquisition – an ecclesiastical tribunal which had tremendous power to interrogate and torture witnesses who were suspected of religious heresy. The inquisition was led by Isabella’s confessor the fanatical Thomas de Torquemada. The Inquisition was approved by the Vatican, but Isabella and Ferdinand developed strong control over its direction – making it into an effective means to control loyalty to the Catholic Monarchy and the Spanish state.

The Inquisition gradually saw its scope widen, and during their reign, thousands were arrested and subject to torture and punishments. Targets included former Jews and Muslims who were suspected of practising their old religion. It also included anyone who was perceived to have ‘unorthodox’ views of the Catholic religion. The inquisition’s power was very successful in stifling any opposition to the Monarch on either religious or political grounds. As a consequence, Spanish feudal Lords lost most of their influence. It also stifled intellectual discovery as people feared that expressing different points of view – even in science or the arts could be the object of investigation. Some scholars have suggested the inquisition had a long-lasting impact on Spain – slowing down innovation and discoveries over the next few centuries. It was also one reason why Protestantism never gained a foothold in Spain. In 1492, the inquisition started to target the Jewish community. All 80,000 Jews in Spain were forced to convert or flee the country. Many Jews died during their expulsion and the loss had repercussions for the economy.

Conquests in the Americas

Isabella and Ferdinand played a prominent role in allowing, encouraging and rewarding explorers who travelled to the Americas. Initially, for the purposes of exploration, it soon became about exploiting the lands for wealth and then claiming lands for the Spanish crown. She did not approve of enslaving people from the Americas (though she did support enslaving Africans), but her wishes were mostly ignored.

One of the most momentous moments in her reign occurred when Isabella agreed to sponsor the expedition of the Genevian Christopher Columbus to the Americas in 1492. Despite only requesting a modest sum, many people had already turned Columbus down. Isabella’s decision to give Columbus the go-ahead enabled Spain to get a head start in claiming lands in the Americas. Technically, Columbus was not the first European to reach American soil, but Columbus’ mission was of tremendous importance because it led to the first European settlements – and encouraged by the success of Columbus – soon many more adventurers were wanting to sail across the Atlantic in the hope of name and fame.


Isabella gave birth to one son, four daughters (and two children stillborn). Despite rejecting an arranged marriage herself, Isabella arranged for her daughter Juan to marry Philip I, heir to the Hapsburg Empire and the kingdom of Burgundy. Isabella’s grandson, Charles V, went on to become the Holy Roman Emperor and king of the largest empire in Europe. Charles V continued his grandmother’s legacy of ardently supporting the Catholic faith. Another of her daughters was Catherine of Aragon, who was married to Henry VIII. Her staunch Catholic upbringing meant she refused to divorce Henry when she failed to produce male heir. This decision would lead to England splitting from the Roman Catholic church.

Isabella lost two children in childbirth or stillborn. One child was lost due to undertaking a strenuous journey on political business. She was sanguine about death; even when she lost her only son Prince John in 1497 she remarked: “The Lord gave and the Lord hath taken away: blessed be the name of the Lord.”


Isabella I of Castille died on 24 November 1504, after a long period of illness. She suffered from fever and dropsy. During her last 50 days, she prayed frequently and wrote a will which told her successors to continue her legacy of honouring and defending the Church, continuing with the inquisition and the fight against ‘depraved heretics’. She also called for the conquest of Africa. An extra addition, a day before her death asked for Indians in America to be treated fairly.

Citation: Pettinger, Tejvan. “Biography of Queen Isabella I”, Oxford, UK.  www.biographyonline.net. Published 20 June 2019. Last updated 6 November 2019.

Game of Queens: The Women Who Made Sixteenth-Century Europe

Book Cover


Game of Queens: The Women Who Made Sixteenth-Century Europe by Sarah Gristwood at Amazon


IsaacNewton- 100 most influential people – A list of 100 most influential people as chosen by Michael H. Hart, from his book 100 most influential people in the world. Includes; Muhammad, Jesus Christ, Lord Buddha, Confucius, St Paul and Johann Gutenberg.

Mariecurie Women who changed the world – Famous women who changed the world. Features female Prime Ministers, scientists, cultural figures, authors and royalty. Includes; Cleopatra, Princess Diana, Marie Curie, Queen Victoria, and Joan of Arc.

politicians Royalty – Famous Kings and Queens throughout history. Including Henry VIII, Tsar Nicholas II, Queen Victoria and Catherine the Great.