||This chapter presents the premise that social class is a potent, robust, and distinct predictor of how people think and act in organizations. Drawing on theories of social cognition, I define social class as a dimension of the self that is rooted in objective material resources (via income, education, and occupational prestige) and corresponding subjective perceptions of rank vis-à-vis others. Informed by demonstrations of the psychological effects of social class, I describe how social class may shape behavior in three illustrative domains of organizational life: social relationships, morality, and judgment and decision-making. I document objective and subjective measures of social class to guide research on its effects. I conclude by discussing the risks and benefits of investigating the social class of organization members, and the potential costs for organizations and researchers who ignore social class.