The legitimacy of governments has been an issue for rulers in Iran from the past to the present. Legitimacy is a relative issue for all governments, and no government has had and will never have complete and absolute legitimacy. Many governments in Iran have also grappled with the issue of legitimacy and have even faced a crisis in this regard. Despite the military power of Cairo and the victory over the occupying enemies, the government of Nader Shah faced the issue of legitimacy from the very beginning of the Afshari dynasty, and over time this issue turned into a crisis of legitimacy. Using the historical method, this article seeks to answer the question of what were the causes and contexts of the crisis of legitimacy of the Naderi government and what was Nader's reaction to this crisis? The findings of the research suggest that two types of causes and contexts, originary and functional, caused problems and then crises in the legitimacy of Naderi's government. From the originary perspective, the existence of a deep-rooted rival legitimacy and the lack of lineage legitimacy were challenges that Nader always struggled with. According to the findings of the present study, functional legitimacy was a much more important factor that caused the erosion of legitimacy and made it critical. Performance based on tyranny, inefficiency and dysfunction of the government, crisis in identity and participation, attempts to transform the foundations of religious legitimacy, and the rupture of the knowledge-power relationship in legitimation were among the main causes of the crisis in the legitimacy of the Naderi government.
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