Isabella of Portugal (Isabel in Portuguese and Spanish) (1428 – 15 August 1496) was Queen of Castile and León between 1447 and 1454 as the second wife of King John II.
A granddaughter of John I of Portugal and Philippa of Lancaster, Isabella married John at age 19. They had two children that survived infancy: Isabella, who became Isabella I of Castile, and Alfonso, who died young.
Isabella was born c. 1428 in the Kingdom of Portugal. Her father was Infante John, 3rd Constable of Portugal, a younger son of King John I of Portugal and Philippa of Lancaster. Her mother, Isabella of Barcelos, belonged to the House of Braganza as the daughter of Afonso, 1st Duke of Braganza and his first wife, Beatriz Pereira de Alvim. John and Isabella were uncle and niece.
Isabella was brought up at the Portuguese royal court, but little is known of her early life before her arrival in Castile.
Following the death of Maria of Aragon on 18 February 1445, John II of Castile was left a widower with only one child, the future Henry IV of Castile. Henry had been joined to Blanche II of Navarre in an unconsummated marriage for seven years and was called "El Impotente." Because of this, John decided to seek another wife, and originally intended to marry Princess Radegonde, daughter of Charles VII of France. However, John's trusted adviser and friend, Álvaro de Luna, sought to develop a political alliance with Portugal and regarded Isabella of Portugal as an ideal candidate to strengthen it. Apparently without John II's knowledge, de Luna and Peter of Coimbra began arranging the marriage between the king and Isabella.
Within only a few months of María of Aragon's death, the marriage negotiations had already been concluded. The couple were first cousins once removed through the king's mother Catherine of Lancaster, who was half-sister of Philippa of Lancaster, Isabella's paternal grandmother.
Because the prospective spouses were related within the third degree of consanguinity, Pope Eugenius IV issued an apostolic brief dispensing them from the impediment of kinship. The brief was dated at Rome on 5 November 1445.
The first successful negotiations took place at Ávila on 2 April 1446, when agreements concerning Isabella's dowry were signed. On 9 October, the formal betrothal was concluded at Évora. In addition to defining the terms of the marriage, the agreement addressed the considerable age difference between the couple—John was forty-one and Isabella eighteen—and specified the arrangements that would apply should she become a widow. She would be free to return to Portugal and remarry without forfeiting either the lifetime revenues assigned to her or the three million maravedís granted to her by the Crown of Castile upon her marriage. She was also guaranteed complete authority over the administration of her own household.
The betrothal was celebrated in Portugal in May 1447 with elaborate festivities in Lisbon, Coimbra, and Pinhel. From there she was escorted by a Castilian retinue to Madrigal de las Altas Torres.
On 22 July 1447 Isabella married John II at the royal palace of Madrigal de las Altas Torres. The ceremony was officiated by Pedro of Castile, the king's uncle and Bishop of Palencia. One of the witnesses to the marriage was Íñigo López de Mendoza, Marquis of Santillana, who later dedicated to the queen a poem beginning, "May God make you virtuous, blessed Queen, as much as He has made you beautiful," in which he also mentions the painter Giotto.
King Afonso V of Portugal provided Isabella with a dowry consisting of the 45,000 florins owed to Portugal by Castile, together with an additional 60,000 florins representing her inheritance, which was to be paid upon her mother's death. In return, John II granted her three million maravedís, an annual income of 1,350,000 maravedís, and the lordships of Soria, Arévalo, and Madrigal. Although Ciudad Real was also included among her grants, she appears never to have taken possession of it. She formally took possession of Madrigal on 2 August and of Soria on 14 August.
Isabella arrived in Castile from Portugal in the same month as her marriage, accompanied by a large retinue of ladies-in-waiting, including Beatrice of Silva, who became renowned at the Castilian court for her beauty and later founded the Order of the Immaculate Conception and was canonized by the Catholic Church. Also among her attendants was Catalina Franca de Castro, daughter of the knight Juan de Franca y Alarzón, who served as her menina, lady-in-waiting, and chief lady of the household. Catalina became the queen's closest confidante following her arrival in Castile. Together with her husband, Gutierre Velázquez de Cuéllar (1430–1492), she managed the queen's household until the king's death.
During her early years as queen consort, court life revolved around hunting, banquets, and dances. Contemporary sources portray her as a politically capable figure. Her library included a copy of the Memorial de Virtudes by Alonso de Cartagena, a treatise dedicated to her by its author that emphasized the ruler's responsibility to make just decisions for the benefit of his subjects.
Following the birth of her daughter in 1451, Isabella's her mental health began to deteriorate, and contemporaries considered her to be suffering from mental illness. Her condition reportedly worsened after the birth of her second child and deteriorated further following her husband's death. Modern medical interpretations have identified her symptoms as consistent with postpartum depression. Her mental illness has also been attributed to hereditary factors within the Portuguese royal house.
Contemporary chronicles describe her marriage as a close and affectionate one. According to Cañas Gálvez, John II found in her the beauty and affection that he had not experienced in his marriage to Maria of Aragon. Chroniclers also recorded public displays of affection between the royal couple, crediting her with rejuvenating the king's spirits. When she began to show signs of emotional instability, the king attempted to lift her spirits with gifts, including "a gold chain fashioned in the form of tree trunks, with fifty-eight links enamelled in white, grey, and rose, weighing six marks and one ounce", as well as an annual income of 6,000 maravedís.
Isabella played a significant role in the downfall of Constable Álvaro de Luna. Luna was deeply unpopular at court and especially loathed by Isabella because of the influence he exercised over John II.
In 1453, de Luna had John's chief auditor thrown out of a window. John was convinced by Isabella to have de Luna arrested and executed. John supposedly regretted the execution, and his health declined in the months after.
John II of Castile died in Valladolid on 22 July 1454. In his will, he appointed Isabella as guardian and administrator of the persons and estates of their children, Isabella and Alfonso, provided that she remained in his kingdoms and did not remarry, effectively obliging her to remain in Castile. Although her marriage capitulations had allowed her to return to Portugal and remarry, they made no provision regarding any future children, and she never returned to live in Portugal. Shortly before his death, influenced by Juan Pacheco, Marquis of Villena, and possibly in an effort to prevent another civil war, John II confirmed as his heir his son by his first marriage, who succeeded him as Henry IV of Castile. Henry's marriage to Blanche II of Navarre had been annulled the previous year, and in 1455 he married his cousin Joan of Portugal, who was also a cousin of the dowager queen Isabella.