To explain the legitimation of inequality among the members of a social system, we blend system justification theory and the theory of social judgment. We identify adaptation and replacement as two major mechanisms of inequality legitimation and examine their influence in the unique setting of a natural experiment, the reunification of socialist East Germany and capitalist West Germany. We show that the new members of a society in which inequality is broadly endorsed and perceived as enduring will adapt to this perception and come to view inequality as acceptable. This process of adaptation reflects the subtle but powerful influence of collective legitimacy on an individual's tacit approval of inequality. Inequality also becomes legitimate as older cohorts are replaced by younger cohorts; however, this effect is weaker than the effect of adaptation. We contribute to the literature by demonstrating that developing and testing a theory of how inequality becomes legitimized can provide new insights into the ideational antecedents of inequality. This article is protected by copyright. All rights reserved.