We are in the middle of a planetary crisis that urgently requires stronger modes of earth system governance. At the same time, calls for justice are becoming increasingly pronounced in sustainability research: there can be no effective planetary stewardship without planetary justice. Rapid planetary-scale processes have reinforced and further created vast injustices at international, national, and subnational levels. Often, the burden has fallen most severely on the poor and marginalized communities. Yet the literature on planetary justice tends to stay at the level of ideal conceptions and abstract normative arguments of justice theory, without an explicit concern for the needs of the poor. In this Perspective, we focus discussions of planetary justice on the needs of the poorest. We discuss whether the dominant approaches to planetary stewardship and earth system governance are apt at realizing a pro-poor vision of justice and what alternative approaches might be needed.