Food-based dietary guidelines (FBDGs) provide country-specific guidance on what constitutes a healthy diet. With increasing evidence for the synergy between human and planetary health, FBDGs have started to consider the environmental sustainability of food choices. However, the number of countries that discuss environmental sustainability in their guidelines is unknown. The purpose of this Review was to identify countries with government-endorsed FBDGs that made explicit mention of environmental sustainability and to examine the breadth and depth of the inclusion of sustainability in FBDGs. The Food and Agriculture Organization of the UN identified 95 countries with FBDGs. We assessed 83 countries against our inclusion criteria, of which 37 mentioned environmental sustainability. Relevant content was assessed against a set of criteria based on the Food and Agriculture Organization's guiding principles for sustainable healthy diets. The depth to which environmental sustainability was discussed varied and it was often restricted to general explanations of what a sustainable diet is. Few FBDGs addressed why sustainability is important, how dietary changes can be made, or provided quantified advice for implementing sustainable diets.