A model of authoritarianism on a group level of analysis based on Duckitt's concept of authoritarianism is presented. This conceptualization is called group authoritarianism (GA), which is defined as the belief about the appropriate relationship that should exist between groups and their individual members. The process model of group authoritarianism connects traditional authoritarianism theories with the Social Identity Approach. According to this model group-authoritarianism reflects the situation-specific activation of an authoritarian disposition in group contexts. Thus, group authoritarianism provides a perspective according to which personality characteristics and general psychological mechanisms described by Social-Identity Theory (SIT) and Self-Categorization Theory (SCT) interact in predicting intergroup hostility and intergroup discrimination. This article describes the development of a group authoritarianism scale as well as an experimental study that tests the main assumption of the group authoritarianism process model. The results confirm the reliability and validity of the group authoritarianism scales and the main hypothesis of the group authoritarianism model.