Rostam, the Iranian paladin, has undergone numerous semantic transformations in the transition from historical narratives to the national epic. Drawing upon the concepts of sacred time and the paradigmatic nature of myth (Eliade) as well as discourse analysis (Foucault), this article conducts a comparative study of the evolution of Rostam's image in historical texts before and after the Shahnameh. The main research question investigates how Rostam's image was reflected in early historiographical accounts and what influence Ferdowsi's narrative had on subsequent historiography. For this purpose, fourteen historical texts were examined using qualitative content analysis and a comparative approach. The findings indicate that in pre-Shahnameh texts, Rostam appears as a marginal figure lacking narrative coherence; in these texts, he is either reduced from the sacred time of myth to the ordinary time of history, transformed through religious interpretation into the opposition of two religious discourses, or occasionally brought closer to the realm of myth through a return to archetypal elements such as Simorgh. In post-Shahnameh histories, three distinct patterns can be identified: structural adaptation and acceptance of the Shahnameh's discursive framework, ideological reproduction in service of the dominant power discourse, and semantic depletion in which Rostam's name is reduced to a floating signifier and a tool for panegyric. The conclusion is that Ferdowsi's Shahnameh, by integrating scattered narratives and returning Rostam to sacred time, became the principal and dominant reference for the representation of this hero in the collective memory of Iranians, and subsequent texts, even in cases of distortion or reduction, have operated within its discursive framework.