In this paper, we argue that the role of the underground has been discursively absent from contemporary debates about the Anthropocene. We build on recent geographical scholarship that has challenged ‘surface bias’ and call for geographical debate to go deeper into the third dimension; to explore the Subterranean Anthropocene; to embrace volume ontologies. We present three core arguments. (1) The Anthropocene is about our future underground, a geological epoch signifier where stratigraphic signatures will be etched in future rocks. This requires us to critically reflect on how our human identity and practice is entangled with rock stratum, both now and in the future. (2) The Anthropocene is about our subterranean past. It involves the emergence of capitalisation and industrialisation – two major driving forces of epochal change – that are predicated on new technologies that redefine the underground as an epistemological space for economic, social and political calculation. (3) We propose that the Anthropocene is about our current sub‐surface relations. That the underground matters in contemporary society as a resource, as a site of urban infrastructure, as a source of soils for agriculture and as a dump for waste, among many other uses. However, this important protagonist role in society, and hence the Anthropocene, is still somewhat obscured. There is therefore a need for new metaphorical tropes to bring the underground into contemporary environmental discourses. As such, we conclude, subterranean spaces should become more prominent epistemic, physical, technical and conceptual locations for geographical exploration and political geo‐ecological framings.