Humans maintain romantic relationships for sexual gratification, child care assistance, intimate friendship, and a host of other interpersonal benefits. In monogamous relationships (i.e., exclusive courtship between two people), individuals agree that certain benefits of the relationship (i.e., sexual contact, material resources, and emotional support) may only be shared within the pair-bond. That is, each partner is expected to maintain the relationship by provisioning sufficient benefits to satisfy the needs and desires of their partner. By comparison, consensual nonmonogamy (CNM) is a collection of relationship practices and structures whereby partners agree that it is permissible to have sexual contact or form intimate attachments with other people to satisfy these interpersonal needs and desires. In this chapter, we review literature examining who pursues CNM, how people who practice CNM derive and maintain satisfaction within their relationship(s), and when and how these relationships persist. We consider the role of CNM relationship maintenance practices, personality features that predispose people to CNM, and psychological and social barriers (e.g., jealousy, interpersonal conflict, sexual health anxiety, and condemnation) that prevent people from pursuing or maintaining CNM. Throughout, we consider how CNM compares to infidelity as an alternative strategy for pursuing multiple, concurrent romantic or sexual relationships. We close by discussing current directions in the scientific study of CNM and highlight which gaps in the literature are most pressing to address.