She is said by Iberian Muslim sources to have been the daughter-in-law of Al Mutamid, the Muslim King of Seville, wife of his son Abu al Fatah al Ma'Mun, Emir of Cordoba, (d. 1091). Later Iberian Christian chroniclers call her Al Mutamid's daughter, but the Islamic chroniclers are considered more reliable. With the fall of Seville to the Almoravids, she fled to the protection of Alfonso VI of Castile, becoming his mistress, converting to Christianity and taking the baptismal name of Isabel.
She was the mother of Alfonso VI of Castile'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 may have been 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 moved to Leon where the sepulchre and inscription can now be found. A second inscription memorializes Queen Isabel, making her 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.
^Bernard F. Reilly, The Contest of Christian and Muslim Spain, 1031-1157, (Blackwell, 1995), 92.
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Alberto Montaner Frutos, "La Mora Zaida, entre historia y legenda (con una reflexión sobre la técnica historiográfica alfonsí)" in Historist Essays on Hispano-Medieval Narrative: In Memory of Roger M. Walker, 272–352 (2005).
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Jaime de Salazar y Acha, "De nuevo sobre la mora Zaida." Hidalguía: la Revista de Genealogía, Nobreza y Armas. 54:225–242 (2007).