Respiratory syncytial virus (RSV) infection is an important cause of infant mortality. Here, we estimated the potential impact of maternal vaccination against RSV on life-threatening RSV infection in infants. We developed a mathematical model for maternal vaccine-induced antibody dynamics and used characteristics of a maternal RSV vaccine currently in phase 3 of clinical development. The model was applied to data from two cohorts of children younger than 12 months with RSV-related paediatric intensive care unit (PICU) admission in the United Kingdom (n = 370) and the Netherlands (n = 167), and a cohort of 211 children younger than 12 months with RSV-related in-hospital death from 20 countries worldwide. Our model predicted that, depending on vaccine efficiency, maternal vaccination at 30 weeks’ gestational age could have prevented 62–75% of RSV-related PICU admissions in the United Kingdom and 76–87% in the Netherlands. For the global mortality cohort, the model predicted that maternal vaccination could have prevented 29–48% of RSV-related in-hospital deaths. Preterm children and children with comorbidities were predicted to benefit less than (healthy) term children. Maternal vaccination against RSV may substantially decrease life-threatening RSV infections in infants.