Pedro de Atarés (c. 1083 in Borja – 21 February 1151[1]) was a Spanish noble and member of the House of Aragón.

[1] Pedro inherited the lordships of Atarés and Javierrelatre from his father, and received Borja by gift of King Alfonso VII of Castile,[6] He was one of the claimants to the throne of Aragón after the childless death of King Alfonso I the Battler.

[6] According to the Crónica de San Juan de la Peña, written in the 14th century, he had been the preferred candidate of the Aranonese barons but he then alienated them with his haughty behavior at the assembly, and they instead chose the deceased king's brother Ramiro II, until then a monk.

Although he died without leaving any children,[2] members of the House of Borgia invented a genealogy tracing their origins back to this member of the royal house coinciding with the third wedding of Lucrezia Borgia to Alfonso I d'Este, Duke of Ferrara, which was arranged by her father Pope Alexander VI.

[13] Nevertheless:The legend spread by the family that the Borgia were descendants of this gentleman of royal blood, Don Pedro de Atarés (...), lord of Borja which entitled them to use the double crown of Aragón in their coat of arms, is false.