, , , , ,

Carlos, Prince of Asturias (8 July 1545 – 24 July 1568), was the eldest son and heir-apparent of King Felipe II of Spain. His mother was Infanta Maria Manuela of Portugal, daughter of João III of Portugal and Catherine of Austria an Infanta of Castile and an Archduchess of Austria, the posthumous daughter of King Felipe I by Queen Joanna of Castile.

Carlos was mentally unstable and was imprisoned by his father in early 1568, dying after half a year of solitary confinement.

In 1556, Emperor Charles V abdicated and retired to the Monastery of Yuste in southern Spain, leaving the Spanish holdings of his empire to his son, Felipe II, Carlos’s father. The former emperor died in 1558, and the following year, Prince Carlos was betrothed to Elizabeth of Valois, eldest daughter of King Henri II of France and Catherine de’ Medici. However, for political reasons, and his father’s mistrust of Carlos’s temper, she instead married his father, King Felipe II, in 1560, as his third wife.

Elizabeth de Valois of France

His health was always weak. At age 14 he fell ill with malaria, which provoked severe deformations in his legs and spinal column. In 1561 the doctors of the court recommended that he move permanently to Alcalá de Henares for his health, as the climate was milder.

Carlos constantly complained about his father’s resistance to giving him positions of authority. Finally, the King gave him a position in the Council of Castile and another in the Council of Aragon. This only made Carlos more furious, since both organisations were important but ultimately consultative. He showed no interest in the councils or in familiarising himself with political matters through them.

Three other brides were then suggested for the Prince: Mary, Queen of Scots; Margaret of Valois, youngest daughter of Henri II of France (sister of his step-mother); and Archduchess Anna of Austria, who was later to become Felipe’s fourth wife, and was a daughter of Felipe II’s cousin, Emperor Maximilian II and Felipe II’s sister Infanta Maria of Spain.

It was agreed in 1564 that Carlos should marry Archduchess Anna. His father promised him rule over the Low Countries in 1559, before his accident, but Carlos’s growing mental instability after it, along with his demonstrations of sadism, made his father hesitate and ultimately change his mind, which enraged Carlos further.

The 15-year-old Carlos was recognised in 1560 as the heir-apparent to the Castilian throne, and three years later as heir-apparent to the Crown of Aragon as well. Also, had he lived until the onset of the Portuguese succession crisis two decades later, he would have had a better claim to the Portuguese throne (in the aftermath of the extinction of the House of Aviz) than his father as he was the eldest surviving grandson of King João III of Portugal.

Because of his eminence, he often attended meetings of the Council of State (which dealt with foreign affairs) and was in correspondence with his aunt Margaret, who governed the Low Countries in his father’s name.

In 1567, the prince gave new proofs of mental instability. During a walk, water thrown from a window accidentally splashed him. He ordered the house to be set on fire. He tried to stab and kill the Duke of Alba in public and in broad daylight. He tried to throw a servant who bothered him through the window of the highest floor of the palace, and also tried to kill a guard who had also displeased him that same year.

In the autumn of 1567, he made another attempt to flee to the Netherlands by asking Johann of Austria to take him to Italy. Johann was loyal to the king and aware of Carlos’s mental state. He asked for 24 hours to think about it and used them to reveal the plan to the king who immediately denied permission for the trip.

As a consequence, Carlos tried to murder Johann. He loaded his gun and called Johann of Austria to his room, where he tried to shoot him repeatedly. The attempted assassination was fruitless because one of the servants, knowing the prince full well, had discharged the gun while the prince called Johann.

Carlos grew so irate that he tried to attack Johann with his bare hands. He eventually informed various people in court of his desire to murder the King. There is debate about whether he actually tried to do so. After that incident, King Felipe II imprisoned the prince in his rooms without receiving correspondence and with limited contacts with the exterior world.

Just before midnight on January 17, 1568, Felipe II, in armour, and with four councillors, entered Don Carlos’ bedchamber in the Alcázar of Madrid where they declared his arrest, seized his papers and weapons, and nailed up the windows. Since Carlos threatened to take his own life, the king banned him from having knives or forks in his room. Carlos then tried to starve himself, but this also failed.


When it came to explaining the situation to public opinion and European courts, Felipe II tried to explain his son’s absence without disclosing his actual faults or mental condition, in hopes of an eventual recovery.

This lack of transparency was used to fuel the anti-Imperial propaganda of Prince Willem I the Silent of Orange. On July 24, 1568, the prince died in his room, probably as the result of his delicate health. His death was used as one of the core elements of the Spanish Black Legend in the Netherlands, which needed to justify a revolt against the king.

It was later claimed that he was poisoned on the orders of King Felipe II, especially by Willem in his Apology, a 1581 propaganda work against the Spanish king. The idea of the poisoning had been held by central and north European historians, based on the pieces of propaganda produced in the Netherlands, until the 20th century, while most Spanish and Italian historians kept claiming that evidence and documentation pointed at a death by natural causes.

Modern historians now think that Carlos died of natural causes. Carlos grew very thin, and some had interpreted his hunger strikes as an eating disorder developed during his imprisonment, alternating self-starvation with heavy binges.