Constance of Portugal (pt: Constança; 3 January 1290 – Sahagún, 18 November 1313; Portuguese pronunciation: [kõʃˈtɐ̃sɐ]), was Queen of Castile by her marriage to Ferdinand IV.

Finished with the Valladolid Courts of 1295, María de Molina, Dowager Queen and Regent of the Kingdom of Castile, in the name of her son Ferdinand IV and Henry of Castile the Senator, co-regent of the Kingdom, had a meeting with King Denis of Portugal in Ciudad Rodrigo, where the Queen-Regent surrounded several strongholds in order to end the hostilities between both Kingdoms; in addition, the betrothal between Ferdinand IV and Constance was confirmed, and also the future marriage between Ferdinand IV's sister Beatrice with Constance's brother and heir of the Portuguese throne, Afonso was arranged.

Five years later (1307), shortly after the birth of their first-born child, a daughter called Eleanor (future Queen consort of Aragon), the Castilian King, who was besieging the city of Tordehumos which housed the rebellious magnate Juan Núñez II de Lara, chief of the House of Lara, sent his wife and newborn daughter to request a loan from her father, King Denis.

[1] During the Valladolid Courts of 1307, where Constance didn't participate, Ferdinand IV tried to end the abuses of the nobility, correct the administration of justice and soften the tax pressure over the Castilians.

The next year (1308), the Queen gave birth to a second daughter, named Constance after her, who died in 1310, aged 2 and was buried in the disappeared convent of Santo Domingo el Real.

Because of the high temperature during the month of his death, Peter, Lord of Cameros and brother of the late King and the now Dowager-Queen Constance decided that his remains would be buried in the Mosque–Cathedral of Córdoba.

The body of the King was deposited in the major chapel of the cathedral by disposition of his wife, and it was also decided that six chaplains would pray every night before his tomb during the month of September in the anniversary of his death, in perpetuity.

At the same time, the prelates and procurators who supported the Lord of Cameros and María de Molina agreed to meet in the church of San Francisco at Palencia, of the Order of the Franciscans, while the supporters of the Lord of Valencia de Campos reunited in the convent of San Pablo of Palencia, of the Order of the Dominicans, linked to the House of Lara.

The double Cortes of Palencia of 1313 gave origin to two different orders: one of them granted by the Lord of Valencia de Campos, as tutor of Alfonso XI, to the councils of Castile, León, Extremadura, Galicia and Asturias —territories in which predominated his own supporters—; and the other promulgated by Queen María de Molina and her son, the Lord of Cameros, as joint tutors of Alfonso XI, and delivered at the request of the councils of Castile, León, Toledo, Extremadura, Galicia, Asturias and Andalusia.

In the meanwhile, both sides tried to reach a definitive agreement on who should be the guardian of the infant King, intervening in the negotiations the Masters of the Orders of Santiago and Calatrava, as well as Don Juan Manuel, supporter of John of Castile.

However, at the end of 1313 Peter was informed of the defeat of the Granadian sultan and, during his return to Castile, besieged for three days and took the castle of Rute, located in Córdoba.

VITAE FINIS DIE XXIII NOV. Aº MCCCXIIIThe epitaph, roughly translated says: "Here lies Queen Constance, wife of King Ferdinand IV.