Mortality inequalities remain substantial in many countries, and large shocks such as pandemics could amplify them further. The unequal distribution of COVID-19 confirmed cases suggests that this is the case. Yet, evidence on the causal effect of the epidemic on mortality inequalities remains scarce. In this paper, we exploit exhaustive municipality-level data in France, one of the most severely hit country in the world, to identify a negative relationship between income and excess mortality within urban areas, that persists over COVID-19 waves. Over the year 2020, the poorest municipalities experienced a 30% higher increase in excess mortality. Our analyses can rule out an independent contribution of lockdown policies to this heterogeneous impact. Finally, we find evidence that both labour-market exposure and housing conditions are major determinants of the epidemic-induced effects of COVID-19 on mortality inequalities, but that their respective role depends on the state of the epidemic.