BIOGRAPHY
Zaida of Seville is said by Iberian Muslim sources to have been the daughter-in-law of Al-Mutamid, the Muslim emir of Seville, wife of his son Fath al-Mamun, emir of Cordoba, who died in 1091. Later Iberian Christian chroniclers call her Al Mutamid's daughter, but the Islamic chroniclers have been considered more reliable. For political reasons Al Mutamid was said to have been a descendant of the prophet Mohammed. Recently strong evidence has emerged that Zaida's first husband was also her first cousin, her (reputed) father and her father-in-law being brothers. If this evidence were true, as well as the claim relating to her father and father-in-law's descent, it would make Zaida also a descendant of Mohammed, but the latter claim is unlikely to be true.

With the fall of Seville to the Almoravids, Zaida fled to the protection of Alfonso VI 'the Brave', king of Castile and León, becoming his mistress, converting to Christianity and taking the baptismal name of Isabel.

She was the mother of Alfonso's only son Sancho who, though illegitimate, was named his father's heir, but was killed in the Battle of Uclés of 1108 during his father's lifetime. It has been suggested that Alfonso's fourth wife Isabel was identical to Zaida, but this is still subject to scholarly debate, others making Queen Isabel distinct from the mistress or suggesting that Alfonso had two successive wives of this name, with Zaida being the second Queen Isabel. Alfonso's daughters Elvira and Sancha were by Queen Isabel, and hence were possibly Zaida's.

She died in childbirth, and it is unclear whether the child being delivered was Sancho, Sancha or Elvira (the younger of the two if Zaida is indeed identical to Queen Isabel, their order of birth not being known), or an additional child, otherwise unknown. A funerary marker once at Sahagun bore the inscription:

_H. R. Regina Elisabeth, uxor regis Adefonsi, filia Benabet Regis Sevillae, quae prius Zayda, fuit Vocata_ ('Queen Isabel, wife of King Alfonso, daughter of Aben-abeth, king of Seville; previously called Zayda.')

The tomb was later removed to León where the sepulchre and inscription can now be found. A second inscription memorialises Queen Isabel, making her the daughter of Louis, king of France (although there was no such king in the generation prior to Queen Isabel). Both memorials are non-contemporary and neither is generally viewed as credible.