AIMS: The aim was to describe the impact of socio-economic inequalities (SEI) on COVID-19 mortality in people aged 45 years and over living with or without diabetes during the two epidemic waves of 2020 (wave 1 (W1): March-May; wave 2 (W2): September-December) in European France. METHODS: People living with pharmacologically treated diabetes were identified using a validated algorithm from the French National Health Data System. COVID-19 mortality in 2020 was obtained from the French Medical Causes of Death database. SEI were measured using the French Deprivation Index at municipality level (FDep; with Q1 corresponding to people living in the least deprived). Age-standardised COVID-19 mortality was calculated by FDep quintiles for each month of the year and by sex. The relative risk of COVID-19 mortality associated with FDep quintiles (with Q1 as the reference) according to diabetes status and epidemic wave was estimated by sex using an adjusted log-linear Poisson model. RESULTS: During W1, when only collective measures were available (lockdown), no social gradient was observed, and it was even the least deprived women with diabetes (Q1) who had a higher risk of COVID-19 mortality. Among men with diabetes, only the most deprived (Q5) had a slightly higher risk of COVID-19 mortality than the least deprived (Q1). The same results were overall found in people without diabetes.During W2, after the implementation of the first individual preventive measures (mask), COVID-19-related mortality followed a positive SEI gradient among men and women with and without diabetes, with higher rates in the most deprived groups (Q5). Moreover, the influence of SEI was greater in women without diabetes in the most deprived groups (Q3, Q4, Q5) than in women with diabetes. CONCLUSION: Our study highlights the importance of integrating the principles of equity, which give consideration to the most vulnerable, into the development of individual prevention measures.