Teresa of Portugal

Infanta Teresa of Portugal (Coimbra, 1181 – Lorvão, June 18, 1250; pron. IPA2|tɨ'ɾezɐ or /IPA|'tɾezɐ/), also known as Tarasia of Portugal and later as "Infanta-Rainha" (Eng. Princess-Queen), was the oldest daughter of Sancho I of Portugal and Dulce Berenguer. She was also wife of Alfonso IX of Castile.

Teresa was the mother to three of Alfonso's children, but when her marriage to Alfonso was declared invalid because of a discovered familial link which proved them to be cousins, she returned to her familial home of Lorvão, Portugal. There, she founded a Benedictine monastery. Soon after, she converted the monastery into a large Cistercian convent, with over 300 nuns.

In 1230, Alfonso died after having several children with a second wife, Berenguela of Castile. This second marriage was also annulled because Berenguela was Alfonso's second cousin. With two invalid spouses, there was dispute among the children as to who would inherit the throne. Teresa stepped in and allowed Ferdinand III of Castile, Berenguela's first son, to take the throne of León. After the succession battle, Teresa returned to Lorvao and finally took her convent vows after years of living as a nun. She died in the convent on June 18, 1250 of natural causes.

On December 13 1705 Teresa was beatified by Pope Clement XI's papal bull "Sollicitudo Pastoralis Offici", along with her sister Sancha of Portugal. Her Catholic feast day is June 17.