The use of the concept of classism has increased in recent decades in psychology. Classism has been defined in various ways that are considered in this encyclopedia entry. Definitions speak to processes by which biases, stereotypes, condescension, prejudice, and discrimination are predominantly expressed downwards within socio-economic hierarchies toward persons occupying socio-economically disadvantaged lifeworlds. Classism involves devaluing such lower-class persons and reinforcing inequitable socio-economic relations between classes in society. Relatedly, research in psychology documents how lower-class persons are more likely to experience barriers to education, employment, healthcare, and upward social mobility. Classism is also associated for lower-class persons with increased stress, anxiety, shame, reduced self-esteem, and reduced well-being. Future theoretical and empirical scholarship regarding the intersections of various “isms” in shaping the consequences of classism present possibilities for deepening our disciplinary engagements with this important concept.