Growing recognition of the Anthropocene era has led to a chorus of calls for Earth System Governance (ESG). Advocates argue that humanity’s newfound sociotechnical powers require institutional transformations at all scales of governance to wield these powers with wisdom and foresight. Critics, on the other hand, fear that these initiatives embody a technocratic impulse that aims to subject the planet to expert management without addressing the political-economic roots of the earth system crisis. This article proposes a more affirmative engagement with existing approaches to ESG while also building on these critiques. While advocates of ESG typically ignore the capitalistic roots of the earth system crisis and propose tepid reforms that risk authoritarian expressions, their critics also have yet to systematically consider the potential for more democratic and postcapitalist forms of ESG. In response, I propose an ecological Marxist approach based on a structural analysis of capitalism as the primary driver of the earth system crisis and an “ecosocialist” vision of ESG that subordinates the market to democratic planning at multiple scales. I argue that an ecological Marxist perspective is needed to foreground the structural political-economic constraints on earth system stability, though existing approaches to ESG can in turn inform ecosocialist strategies for global institutional design and democratization.