Prejudice is an attitude toward a social group and its members that can be expressed as either a negative or positive (e.g., paternalistic) evaluation and creates or maintains hierarchical status relations between groups. The origins of prejudice include individual differences in personality and ideological preferences, socialization experiences relating to exposure to different social norms, and the functional ways that groups relate to one another. Prejudice can be measured directly through self-report measures or indirectly through patterns of behavior or with techniques such as response latency methods. Moreover, implicit prejudice, which is automatically activated, can be distinguished from explicit prejudice, an attitude people know that they hold and may be able to control. Both types of prejudice predict discrimination—the differential treatment of a group or its members—but the strength of these relationships varies as a function of a variety of contextual factors (e.g., social norms). Because of the wide range of forces that shape prejudice and the functional nature of bias, prejudice can be difficult to change. Among the more robust ways to reduce prejudice are strategies that promote frequent, positive contact with members of another group; encourage people to categorize others in ways that emphasize shared group identities; or alter automatic associations underlying implicit bias. The study of prejudice continues to be an important and actively researched topic in social psychology, with contemporary approaches increasingly considering a broader range of micro- (e.g., genetics) and macro-level (e.g., culture) forces that shape the nature of prejudice and its influence on discriminatory behavior.