The importance of human-animal bonds has been documented throughout history, across cultures, and in recent research. However, attachments with companion animals have been undervalued and even pathologized in the field of mental health. This article briefly surveys the evolution of human-animal bonds, reviews research on their health and mental health benefits, and examines their profound relational significance across the life course. Finally, the emerging field of animal-assisted interventions is described, noting applications in hospital and eldercare settings, and in innovative school, prison, farm, and community programs. The aim of this overview paper is to stimulate more attention to these vital bonds in systems-oriented theory, practice, and research. A companion paper in this issue focuses on the role of pets and relational dynamics in family systems and family therapy.