Alfonso XI of Castile

Alfonso XI of Castile
August 13, 1311 – March 26, 1350

Alfonso XI of Castile was born on August 13, 1311, in Salamanca, Castile. The son of King Ferdinand IV and Queen Constance of Portugal, the prince succeeded his father at only a year old. Due to his young age, a regency formed of royal relatives to govern on his behalf. However, several members, including Queen Constance, died over a 14-year period. As a result of the regency’s instability, three relatives split Castile amongst themselves in 1319, causing chaos in the kingdom. During this time, the nobility fought amongst themselves as the Moors (Muslims) raided Castile with little resistance.

In 1325, Alfonso XI came of age and began ruling independently. The 14-year-old king inherited a kingdom in turmoil with many enemies seeking to contain royal authority. Scarred by his traumatic childhood, a determined Alfonso focused on crushing his enemies. To this end, the king ordered many executions of potential enemies, including his uncle, John. John had been of the three men who carved up Castile in 1319. Seeking revenge for his betrayal, the king had his uncle assassinated in 1326.

John’s death did little to calm Alfonso XI’s bloodlust. The king filled his government with lower-class men to strengthen the monarchy’s power. By doing this, Alfonso gained the loyalty of these men and prevented nobles from holding positions. Alfonso also made an agreement with the Cortes (government assembly). The Cortes supported the king against the nobility in exchange for more political power. In turn, Alfonso had many nobles executed in cold blood.

Personal Life

Afonso IV of Portugal
Afonso IV of Portugal

In 1325, Alfonso XI of Castile married Constanza Manuel. However, the marriage only lasted two years before being annulled. The following year, Alfonso married Princess Maria, eldest daughter of King Afonso IV of Portugal. The marriage itself sealed an alliance between Castile and Portugal. Despite the importance of the marriage, the king treated his wife poorly.

In 1330, Alfonso XI took Eleanor de Guzman, a Castilian noblewoman, as his mistress. To make matters worse, the king openly flaunted his affair, embarrassing his wife. After the birth of his heir, Prince Peter, in 1334, Alfonso abandoned Maria in favor of Eleanor. Outraged at his cruelty, Afonso IV threatened to end his alliance with the king unless he returned to Maria. Taking the threat seriously, Alfonso reluctantly left Eleanor. However, the king soon returned to his mistress and their many children.

Foreign Policy


After crushing the nobility and securing his throne, Alfonso XI turned his attention to the Moors. In 1340, the Marinid dynasty of Morocco had taken the Strait of Gibraltar and defeated a Castilian fleet at Algeciras. With the support of the Portuguese, Alfonso reversed the dynasty’s victories and re-took Algeciras after the Battle of Rio Salado in October. The Marinids returned to Africa upon his victory, never invading the Iberian Peninsula again.

Relationship With Other Kingdoms

Alfonso XI would maintain an alliance with Portugal until his death. Although strained at times due to his affair, the king understood the importance of having Portugal as his ally. Outside the Iberian Peninsula, England and France sought an alliance with Castile. Both kingdoms wanted the powerful Castilian navy on their side. Despite their offers, Alfonso remained distant and never committed to either kingdom.

Final Years

During the last decade of his reign, Alfonso XI continued living with his mistress, Eleanor. In the 1340s, the couple had four more children, bringing their total to ten. As the Black Death began making its way through Europe, the pandemic eventually arrived in Castile around 1349. At the time, the king was besieging Gibraltar, a fortified town held by the Moors. Alfonso refused to end the siege despite a breakout of plague in his camp. As a result, the king became infected and succumbed to the disease on March 26, 1350.


Alfonso XI of Castile had a progressive yet bloody reign. Despite his administrative success, the king’s viciousness caused many deaths and the mistreatment of his wife. Alfonso’s favoritism towards his mistress led to her execution after his death by the vengeful queen. The bad blood between both factions only worsened after Eleanor’s execution. After his mother’s death, Henry engaged in a civil war against Maria’s son, Peter, for control of the throne.


Encyclopædia Britannica, inc. (n.d.). Alfonso XI. Encyclopædia Britannica. Retrieved March 4, 2022, from (n.d.). Biography of Alfonso XI. king of Castilla y León . Retrieved February 4, 2022, from


Andy Tree

I'm a European history enthusiast who seeks to share his passion with others. I hope to inform and inspire readers with my posts!

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