Isabella of Portugal (Isabel in Portuguese and Spanish) (1428 – 15 August 1496) was Queen of Castile and León as the second wife of King John II.

Little is known about Isabella's life before her marriage, but it is likely that she received an education at the Portuguese court befitting of a young noblewoman at the time.

Henry had been joined to Blanche II of Navarre in an unconsummated marriage for seven years and was called "El Impotente."

However, his trusted adviser and friend Alvaro de Luna decided a Portuguese alliance was better politically, and negotiated a match with the much younger Isabella.

This sum would revert to Isabella in the event of the death of John II and also enable her to return to Portugal if she so wished.

[5] When after three years of marriage, Isabella had not yet fallen pregnant she decided in 1450 to take a pilgrimage to Toro and the shrine to Saint Maria de la Vega to pray for a child.

De Luna tried to control the young queen as well, even going as far as to attempt to limit the couplings between the amorous king and his bride.

[3] She was permitted to keep her children until 1461, the year in which Henry's second queen, Joan of Portugal, became pregnant with Joanna, Princess of Asturias, supposedly by her alleged lover, Beltrán de La Cueva.

When Henry IV died in 1474, Isabella bypassed the claims of her niece, who had never been considered legitimate, to become Queen of Castile.

[9] After her death, she was interred next to her husband in the crypt under the royal sepulcher, with Alfonso whose tomb is placed to the side in the Miraflores Charterhouse.

In 2006, on the occasion of the restoration of the Charterhouse, an anthropological study of the physical remains of John II, Isabella, and their son, Alfonso of Castile was carried out by researchers from the University of León.