Ethnic conflicts have been among the significant factors undermining political cohesion and impeding state-building in Afghanistan. The central question of this study is how ethnic conflicts have contributed to the weakening and eventual breakdown of Afghanistan’s political structure. The study aims to explain the relationship between ethnic structures, declining state legitimacy, and the reproduction of political instability by drawing on Joel Migdal’s theoretical framework of “Strong Societies and Weak States.” Methodologically, the research adopts a historical-analytical approach based on the examination of documentary sources, historical records, and studies addressing Afghanistan’s political and ethnic transformations. The findings indicate that the concentration of political power within a dominant ethnic group, the limited political participation of other ethnic communities, and the state’s inability to establish inclusive institutions have undermined state legitimacy and weakened its capacity to regulate social relations and distribute resources effectively. Across different historical periods, from earlier governments to the post-Taliban republic and subsequent periods of Taliban rule, the state’s limited engagement with ethnic and local social networks has contributed to intensified identity-based competition, violence, rebellion, and recurring political crises. Moreover, the instrumentalization of social and political cleavages by ethnic elites has reinforced this cycle. The study concludes that inclusive institutions, equitable ethnic participation, and effective mechanisms for power-sharing are essential for mitigating ethnic conflicts and strengthening political stability in Afghanistan.