This chapter defines wildlife criminology as a criminology concerned not only with wildlife trafficking, but considers criminological perspectives on animals and wildlife within a broader context. The introduction provides a definition of wildlife as constituting animals living primarily outside human control or influence; thus distinguished from companion animals who are directly dependent on humans for food and shelter. However, wild non-human animals are affected by human activity in a variety of ways from trafficking in wildlife, through to destruction of habitat, and development that impacts directly on wildlife. Thus, this chapter explains that the book’s focus is on a wildlife criminology that considers a wide range of unlawful and deviant acts that impact on and harm wildlife. It introduces the four interconnected themes used to explore crimes and harms against wildlife - commodification and exploitation, violence, rights, and speciesism and othering.