A systematic review of definitions, narratives, and paths forward for a protein transition in high-income countries identifies 33 articles addressing challenges in reducing environmental impacts of protein production and consumption, providing healthy diets, and preventing adverse effects of industrial livestock systems. The review highlights unclear definitions, conflicting views on protein reduction or replacement, and a lack of attention to systemic change. Three narratives are identified: the consumer narrative focusing on dietary changes, the techno-centred narrative developing efficient protein production systems, and the socio-technological narrative aiming to transition the agri-food system to an alternative protein regime. The protein transition is seen as crucial for sustainability, health, and food security, but lacks a consistent definition. Solutions should consider scale, initiating actors, and expected impact to support complementary approaches. The review emphasizes the need for clear definitions, alignment with challenges, and systemic approaches to ensure effective transitions. The protein transition is a hot topic in political, private, and public discussions, with initiatives in various countries aiming to promote sustainable food systems. The review underscores the importance of addressing environmental, health, and ethical challenges through diverse narratives and solutions.A systematic review of definitions, narratives, and paths forward for a protein transition in high-income countries identifies 33 articles addressing challenges in reducing environmental impacts of protein production and consumption, providing healthy diets, and preventing adverse effects of industrial livestock systems. The review highlights unclear definitions, conflicting views on protein reduction or replacement, and a lack of attention to systemic change. Three narratives are identified: the consumer narrative focusing on dietary changes, the techno-centred narrative developing efficient protein production systems, and the socio-technological narrative aiming to transition the agri-food system to an alternative protein regime. The protein transition is seen as crucial for sustainability, health, and food security, but lacks a consistent definition. Solutions should consider scale, initiating actors, and expected impact to support complementary approaches. The review emphasizes the need for clear definitions, alignment with challenges, and systemic approaches to ensure effective transitions. The protein transition is a hot topic in political, private, and public discussions, with initiatives in various countries aiming to promote sustainable food systems. The review underscores the importance of addressing environmental, health, and ethical challenges through diverse narratives and solutions.