This study aims to analyze the imaginary structures of the Shahnameh based on Gilbert Durand’s theory of myth criticism and to examine the reflection and continuity of these structures in modern Western literature. Durand’s approach, through the articulation of two modes of the imagination the “diurnal regime” and the “nocturnal regime” provides a framework that enables the narratives of the Shahnameh to be examined beyond conventional historical or literary analyses and to be interpreted within symbolic and imaginal systems. In the first stage of the study, the fundamental imaginary structures of the Shahnameh including symbols of light and darkness, heroic patterns, trials, metamorphosis, and the role of liminal beings are identified and classified within the regimes of the imagination. The findings indicate that figures such as Rostam and Esfandiar can be interpreted within the diurnal regime, while characters such as Siavash and Zal are more appropriately understood within the nocturnal regime; together, these dual structures constitute a persistent layer of Iranian mythic imagination. In the second stage, the research investigates the continuity and manifestation of these imaginary structures in modern Western literature. An analysis of selected works of contemporary fantasy literature particularly those of J.R.R. Tolkien, C. S. Lewis, and postmodern writers demonstrates that many of their narrative patterns symbolically overlap with structures found in the Shahnameh. These include the archetype of the singular hero, the battle between good and evil, the trial-based journey, and the presence of transhuman or supernatural guides.