The food-energy-water (FEW) nexus is increasingly emphasized and prioritized as a framework for research, technology, and policy to deal with complex socio-environmental problems. Producing food in sufficient quantity and of sufficient quality, ensuring enough but not too much water, and generating energy, all to meet human needs and desires, requires an understanding of how those goals complement or counteract one another in specific places and through specific processes. FEW nexus research focuses on understanding the interconnections among each system, in order to provide a more complete picture about the causes and consequences of changes within and across aspects of those systems. This paper synthesizes the current state of thinking and research in FEW nexus field. We first overview the systems underpinnings of the FEW nexus as a conceptual framework, and identify the assumptions, similarities and contrasts among the most cited models from current literature. Several analytical approaches – coupled systems, ecosystem services, flows and risk analysis – are emerging as key tools for conducting interdisciplinary FEW nexus research, and we identify their conceptual connections to systems thinking broadly as well as the specific assumptions that each make about the relationships among systems. Finally, based on expert consultations and assessment of current data availability, we highlight several topical areas of contemporary relevance for FEW nexus research at various scales. Characterizing the conceptual, analytical and empirical similarities and distinctions among approaches to FEW nexus research with a starting point for identifying innovative research questions and approaches.