This study had two objectives: - to assess the short- and long-term impacts on mortality of the temporary reduction in the population’s exposure to air pollution resulting from measures taken to limit the spread of the COVID-19 pandemic in the spring of 2020; - to reassess the long-term total burden of air pollution on annual mortality in metropolitan France for the period 2016–2019 in order to put the results into perspective, and more broadly to update the estimates published in 2016 by Santé publique France. Methods: Regarding the first objective, the reduction in exposure to air pollution was estimated by calculating the difference between, on the one hand, the modeled exposure of the population during strict lockdown and the gradual lifting of lockdown measures, and, on the other hand, the simulated exposure that would have been observed in the absence of lockdown measures. For the second objective, the annual average concentration was estimated over the 2016–2019 period. The quantitative health impact assessment (EQIS) method was used to estimate the consequences on mortality in the French population: 1/ in the short term and longer term, the effects of the reductions in PM10/PM2.5 and NO2 levels observed during lockdown, and 2/ in the long term, an estimate of the total burden of pollution over the 2016–2019 period. Results: The restriction of activities during the lockdown in the spring of 2020 led to a reduction in the French population’s exposure to NO₂ and PM, which prevented approximately 2,300 deaths linked to PM2.5 and nearly 1,200 linked to NO₂ over the period from June 2019 to July 2020. The short-term effects were less significant, with approximately 60 deaths prevented due to PM10 and 300 deaths prevented due to NO2. Our study re-assessed the total burden of air pollution on long-term mortality in metropolitan France using the same scenarios and concentration-risk functions as those used in the 2016 Santé publique France study, which estimated 48,000 annual deaths attributable to PM2.5 exposure in 2007-2008. The results of this study highlight the fact that the total burden remains significant, with nearly 40,000 annual deaths attributable to exposure to PM2.5 and nearly 7,000 deaths attributable to exposure to NO2. Conclusion: This study retrospectively estimates the impact on mortality of the reductions in ambient air pollution observed during the first lockdown in the spring of 2020 in metropolitan France. It provides further evidence confirming that, in an unprecedented context that is certainly neither realistic nor desirable for improving air quality in the long term, public policy measures appear to be an effective lever for reducing pollution levels, and thus public exposure and its health impacts. Certain lessons can be drawn regarding public policy measures or behavioral changes (teleworking, modal shift, etc.) that are likely to become permanent features of French society. Furthermore, the results highlight that while mortality linked to ambient air pollution is trending downward, it remains a significant risk factor in France, and efforts to reduce ambient air pollution must therefore be sustained over the long term for all sources of pollution, with a transition that is appropriate yet ambitious.