Background: Obesity contributes considerably to the problem of health inequalities in many countries, but quantitative estimates of this contribution and to what extent it is modifiable are scarce. We identify the potential for reducing educational inequalities in all-cause and obesity-related mortality in 21 European populations, by modifying educational differences in obesity and overweight. Methods: Prevalence data and mortality data come from 21 European populations. Mortality rate ratios come from literature reviews. We use the population attributable fraction (PAF) to estimate the impact of scenario-based changes in the social distribution of obesity on educational inequalities in mortality. Results: An elimination of differences in obesity between educational groups would decrease relative inequality in all-cause mortality between those with high and low education by up to 12% for men and 42% for women. About half of the relative inequality in mortality could be reduced for some causes of death in several countries, often in southern Europe. Absolute inequalities in all-cause mortality would be reduced by up to 69 (men) and 67 (women) deaths per 100 000 person-years. Conclusion: The potential reduction of health inequality by an elimination of social inequalities in obesity might be substantial. The reductions differ by country, cause of death and gender, suggesting that the priority given to obesity as an entry-point for tackling health inequalities should differ between countries and gender.