Forgiveness is a hallmark teaching within monotheistic religions. This Element introduces the topic in three ways. First, it considers the extent to which forgiveness is specific to or constituted by monotheistic beliefs, by a comparison with analogous teaching and practice in Buddhism. Second, the most extensive section explores the grammar of forgiveness shared across the Abrahamic traditions of Judaism, Christianity and Islam - elements of repentance, intercession, and eschatological deferral. This section identifies some of the divergent tendencies or emphases on this topic among those traditions. A third section addresses the role of forgiveness and monotheistic religions in human cultural evolution and the emergence of eusociality. The aim is for the reader to gain an introductory view of monotheism and forgiveness from a comparative religious example, from an internal examination of Abrahamic traditions, and from a developmental, secular perspective.