The concept of “political justice” is a central signifier in Shia political thought and jurisprudence, persistently recognized as a fundamental criterion for evaluating the legitimacy and efficacy of governments. The present study aims to extract and analyze the conceptual model of political justice through a comparative examination of this concept within the intellectual systems of Imam Riḍā (a.s.) and Ayatollah Khamenei. Employing the theoretical framework of “Imamate-Wilayah Theory,” this research is structured using a qualitative, descriptive-analytical method, with data collected through documentary and library-based sources. The findings indicate that although the theological foundations of both thinkers concerning justice share a common origin, differences in historical contexts—namely, presence versus occultation, and opposition versus established governance—have led to functional diversity. Imam Riḍā’s conceptual model, in confronting Abbasid rule, is oriented toward a “legitimacy-assessing approach,” entailing a critique of the usurpatory structure and an emphasis on the inherent correlation between infallibility/justice and political power. In contrast, Ayatollah Khamenei’s model, from the position of leadership within an established Islamic system, centers on a “system-building approach,” the institutionalization of structural justice, the equitable distribution of opportunities, and the linkage of justice with comprehensive progress. Ultimately, it is concluded that the evolution of Shia political thought represents the logical extension of a transition from “demanding and critiquing illegitimate governance” to “institutionalizing and implementing justice within novel, law-governed structures.”