Isabella was born as the daughter of King John II of Castile. She grew up in modest circumstances after her father's death.

King John II died and Isabella's half-brother Henry IV became king. Isabella and her mother were sent to live in the small town of Arévalo.

Henry IV brought Isabella to his court for proper royal education. She learned Latin, philosophy, and the arts of governance.

Through the Treaty of Toros de Guisando, Isabella was recognized as heir to Castile. She now had a legitimate claim to the throne.

Isabella secretly married Ferdinand of Aragon without Henry's consent. This union would eventually unite Spain's two most powerful kingdoms.

Upon Henry IV's death, Isabella proclaimed herself Queen of Castile. Her claim was immediately contested by her niece Joanna.

Portugal invaded Castile supporting Joanna's claim to the throne. Isabella and Ferdinand fought to defend their rule.

The Treaty of Alcáçovas ended the succession war in Isabella's favor. She was now undisputed Queen of Castile.

Isabella and Ferdinand established the Spanish Inquisition to enforce religious orthodoxy. This institution would profoundly impact Spanish society.

Isabella and Ferdinand launched the final campaign against the Moorish Kingdom of Granada. This war would complete the Reconquista.

The surrender of Granada ended eight centuries of Muslim rule in Iberia. Isabella and Ferdinand were hailed as champions of Christendom.

Isabella agreed to sponsor Christopher Columbus's westward expedition. This decision would lead to the European discovery of the Americas.

Isabella and Ferdinand issued the Alhambra Decree expelling Jews from Spain. Hundreds of thousands were forced to convert or leave.

Isabella negotiated the division of newly discovered lands with Portugal. This treaty shaped the colonial history of the Americas.

Isabella suffered the deaths of her son Juan and daughter Isabella. These tragedies deeply affected her final years.

Isabella died after a long illness, leaving a transformed Spain. Her will advocated for humane treatment of indigenous peoples in the Americas.