In this article, we enjoin the United Nations (UN) to forge a path out of our plight of multiple environmental and social crises. With other analysts, we identify ‘overshoot’ – the state in which humanity has substantially outpaced Earth’s capacity to regenerate its natural systems and to absorb our waste output – as the root cause of the existential threats we face. This dangerous condition demands rethinking our relationship with Earth and embarking on scaling down the human enterprise within policy frameworks of equity and rights. We argue that when the UN first articulated its international unity and prosperity mission, it did so within a ‘growth’ paradigm that treats Earth and its nonhuman inhabitants as mere resources at humanity’s disposal. The 1994 Cairo Conference on Population and Development reinforced this agenda, with its sharp turn away from the earlier emphasis on population concerns and their link to environmental protection. Today, it is clear that the UN’s foundational goals of peace, human rights and sustainability flounder within a growth-driven framework of human exceptionalism and nature domination. To correct course and reverse our advanced state of ecological overshoot we urge the UN to lead in contracting the large-scale variables of the human enterprise – population, economy, technosphere – and to resist co-optation by political, ideological and special interest pressures that would derail this mandate.