In this article, I develop and defend the claim that we, humanity, will not be able to get significantly closer to a world in which there is ecologically sustainable human development if we do not tackle economic inequalities head-on. This implies that we should focus not only on poverty but also on the entire distribution of income and wealth, including extreme wealth concentration. For national and international policymaking, this means that reducing economic inequality must be one of the central priorities rather than assuming that it is indirectly covered by other social goals such as poverty reduction or formal equality of opportunities, or assuming that it is a problem that will solve itself over time under globalised neoliberal capitalism.