Carbon mineralisation has the potential to sequester and safely store large amounts of carbon dioxide (CO2). However, this technology has not seen the same level of development as geological storage in sedimentary reservoirs. This is primarily because early work on carbonation of minerals focused on high temperature and pressure process routes, which are cost-prohibitive to accelerate the reaction from geological to industrial time scales. Bacteria-mediated carbon mineralisation of mine tailings  overcomes this impediment because it occurs at ambient temperature and standard pressure and the rock is already crushed. With abundant mafic and ultramafic rock, a highly developed mining sector, and a warm climate that promotes fast carbonation reactions, Australia presents an optimal region to develop this technology. We assess the mineralisation potential of Australia's existing and future nickel mine tailings and estimate that this carbon sink could sequester up to 2,171 Megatons (Mt) of CO2.