Oppression is the antithesis of, and greatest threat to, justice. Oppression is a significant barrier to a society’s quest to be well and healthy. There is continued discrimination against women, lesbian, gay, bisexual, transgender, and queer people, immigrants, and Muslims. This book provides a basic introduction to the psychology of oppression that will be useful in making oppression and social justice education more accessible to more people. It is very timely as it may reach and inform a wider range of people about various forms of oppression and how they influence peoples’ psychological experiences. The book is organized into ten chapters. The first three chapters focus on the fundamentals of oppression. Chapter one provides a brief overview of what oppression is. Chapter two deals with historically and contemporarily oppressed social groups. Chapter three presents historical and contemporary oppression. The next three chapters discuss some of the layers and complexities of oppression. Chapter four covers the evolution of oppression and how oppression may be expressed blatantly or subtly and overtly or covertly. Chapter five describes the three Is of oppression: interpersonal, institutional, and internalized. Chapter six presents the psychological and mental health implications of oppression. The chapters 7 through 9, discuss why oppression exists and continues to persist throughout history. Chapter seven presents the social psychological theories on the existence and persistence of oppression. Chapter eight and nine describes addressing oppression in both clinical and community contexts. The final chapter presents some suggestions about future psychological work on oppression across research, clinical, and community contexts.