Rivers are critical, but often overlooked, parts of food systems. They have multiple functions that support the food security, nutrition, health and livelihoods of the communities surrounding them. However, given current unsustainable food system practices, damming and climate change, the majority of the world's largest rivers are increasingly susceptible to environmental degradation, with negative implications for the communities that rely on them. Here we describe the dynamism and multifaceted nature of rivers as food environments (i.e. the place within food systems where people obtain their food) and their role in securing food security including improved diets and overall health. We also provide a conceptual framework that explain rivers as food environments within the broader food system and describe approaches to characterizing these food environments to better inform our understanding of how they influence food security and nutrition outcomes. Applying this framework to the Mekong River in Cambodia, we describe rivers as multifaceted wild food environments embedded within ecosystems, sociocultural and political environments and sectors of influence. We also explain the ways in which individual factors might influence how communities interact with this food environment. Developing and articulating food-related, ecosystem-specific frameworks and their constructs can guide implementation of policies aimed to improve specific public health or environmental sustainability outcomes. Our conceptual framework incorporates the multiple dimensions of rivers, which will aid future work and public health policy framing to better describe, understand and intervene to ensure protection of rivers' biodiversity and ecosystems as well as food security, health and livelihoods.