The problem of animal suffering is a subset of the problem of evil within the field of the philosophy of religion. Proponents of the problem formulate arguments concluding that the God of monotheism likely does not exist because of the existence of great amounts of non-human animal death, disease, and suffering found both in the natural history of the earth and still today. Major theistic responses to the problem include the denial that non-human animal suffering is morally significant as well as various other theodical explanations providing possible reasons God might want or need to allow animal suffering depending on God’s purposes for creating. The problem of animal suffering is debated within the philosophy of religion, but it is very much so an interdisciplinary issue that concerns not only the philosophy of religion but also theology, biblical studies, animal cognition studies, comparative psychology, ecology, and others. This chapter will introduce the problem of animal suffering, survey the major issues involved in the problem, and then provide a preview of the major sections and chapters in this handbook.