The present article argues that Alfonso X employed the Justinian prophecy of Africa to underscore the Gothic legacy of the Castilian monarchy and to assert that Castilian dominance over Africa was preordained. Alfonso X's vision of Africa was not merely an extension of his crusading efforts, but a complex ideological construct rooted in Gothic and Byzantine traditions. In pledging to defend Africa against Muslim invaders and Christian heretics, Alfonso imitates the actions of Justinian as depicted in the Estoria de Espanna, according to which the latter, in response to a dream featuring Saint Leto requesting his help, pledges to defend Africa against the heretical Vandals. The study also examines how Alfonsine historiography navigated tensions between religious, legal, and dynastic claims to Africa, ultimately shaping a vision of Castilian rule that linked Spain's destiny with Africa's past.