This review focuses on the ways in which the objectification of individuals and groups of people, as well as the self-objectification that typically develops from such treatment, is implicated in positive and negative societal change. Four areas are reviewed: (a) objectification (including dehumanization, infra-humanization, dehumanized perception, sexualization, and colonialism), (b) self-objectification (including double consciousness, internalized oppression, and colonial mentality), (c) genocide and mass violence, and (c) collective action. After reviewing theories in each area, a set of underlying constructs is presented, organized under higher-order categories. Finally, connections between objectification and genocide perpetration, as well as between self-objectification and collective action, are described. It is concluded that the objectification of other people contributes to societal change that runs counter to principles of equality and respect for others, threatens civil rights, and ultimately can result in genocide or mass killings. Furthermore, self-objectification impairs the ability of oppressed groups to act collectively on their own behalf. In contrast, the process of decolonization supports collective action and positive societal change, in part because it liberates oppressed people from self-objectification.