<p>Diets are central components of food systems, and can be thus key entry points for fostering the transformative change needed to meet global sustainability goals. The rapid dietary transitions observed across the world in the past decades are shaped by complex (and often context-specific) factors such as economic transformation, urbanization, and cultural shifts. Despite the substantial variation in their characteristics, drivers and impacts between geographic contexts, there is an emerging consensus that past dietary transitions associated with the increased consumption of animal-sourced products, refined carbohydrates, fats, sugars, and ultra-processed foods have largely had negative outcomes for public health and the environment. There are strong ongoing efforts to promote healthier and more sustainable diets, but challenges persist due to affordability, cultural preferences, and structural constraints. This Special Feature contains seven papers that study different aspects of dietary transitions across diverse geographical contexts. Collectively, the contributions highlight the complex, context-specific drivers and impacts of dietary change, demonstrate that healthy and sustainable dietary alternatives are feasible but involve trade-offs, and emphasize that effective interventions require coordinated, multi-level, and culturally grounded actions.</p>