Tuberculosis is the leading cause of deaths from an infectious disease worldwide. WHO's End TB Strategy is falling short of several 2020 targets. Undernutrition is the leading population-level risk factor for tuberculosis. Studies have consistently found that undernutrition is associated with increased tuberculosis incidence, increased severity, worse treatment outcomes, and increased mortality. Modelling studies support implementing nutritional interventions for people living with tuberculosis and those at risk of tuberculosis disease to ensure the success of the End TB Strategy. In this Personal View, we highlight nutrition-related immunocompromisation, implications of undernutrition for tuberculosis treatment and prevention, the role of nutritional supplementation, pharmacokinetics and pharmacodynamics of antimycobacterial medications in undernourished people with tuberculosis, and the role of social protection interventions in addressing undernutrition as a tuberculosis risk factor. To catalyse action on this insufficiently addressed accelerant of the global tuberculosis epidemic, research should be prioritised to understand the immunological pathways that are impaired by nutrient deficiencies, develop tools to diagnose clinical and subclinical tuberculosis in people who are undernourished, and understand how nutritional status affects the efficacy of tuberculosis vaccine and therapy. Through primary research, modelling, and implementation research, policy change should also be accelerated, particularly in countries with a high burden of tuberculosis.