Relational values-as preferences, principles and virtues about human-nature relationships-have attracted a great deal of attention in recent years. The term has been used to include concepts and knowledge from a wide range of social sciences and humanities, e.g., importantly making space for qualitative approaches often neglected within environmental management and science. Meanwhile, crucial questions have emerged. What counts as a relational value, and what does not? How do relational values (RVs) compare with other value categories and terms, including held, assigned, instrumental, moral, shared, social, and non-material values (e.g., associated with cultural ecosystem services)? In this article, we address these issues, partly by providing context about how the RV term originated and how it has evolved to date. Most importantly, because of their somewhat unique combination of groundedness and moral relevance, positive relational values may offer important opportunities for the evolution of values that may be necessary for transformative change towards sustainability. The special issue includes contributions that contemplate particular concepts (e.g., care, stewardship, eudaimonia-human flourishing), applications (e.g., environmental assessment, environmental policy design), and the history of relevant scholarship in various intellectual traditions (e.g., ecological economics, human ecology, environmental education). Together with this suite of thought-provoking papers, we hope that the clarification we provide here facilitates a broad and productive interdisciplinary exchange to create and refine a reflective but powerful tool for sustainability and justice.