While the political and ideological uses of eschatology in the Byzantine, Carolingian or Ottonian worlds are well studied, the adaptation of these discourses in the Iberian Peninsula is generally little known. This article examines the link between the adoption, at the end of the eleventh century, of the title of emperor by the kings of Castile-León and their political uses of a prophetic and apocalyptic discourse to legitimize the war against Islam until the 13th century. Unlike Carolingian or Byzantine constructions, the mechanisms of legitimation and exaltation of the Iberian rulers do not employ the legend of the Last Emperor. The 12th century chronicles instead continue to emphasize the figure of the penitent king, pious and respectful of the Church, in close connection with a monastic conception of eschatology which has been a major dimension of discourse of royal legitimation since 711.