Rapid increases in human population and per-capita waste production have resulted in accelerated growth in the size and number of landfills. We propose that microbiota within landfills can contribute to a better understanding of the Anthropocene thus far. Because landfills are characterized by conditions that are uncommon in natural, non-anthropogenic environments, they present a novel, rapidly growing, and essentially unstudied ecological system. Anthropogenic impacts may lead to unique adaptations in resident microbial communities, resulting in novel assemblages, activities, and features that differ from those in natural environments. Modern tools like molecular and bioinformatic techniques allow scientists to characterize these communities in unprecedented detail. A nuanced understanding of the adaptations, such as novel degradation abilities, that arise from such unusual selection pressures could facilitate improvements in bioremediation. Furthermore, similarities between landfill formation and geological deposition processes suggest that landfills will be preserved in future geological records and, consequently, may be suitable for dating anthropogenic influences at the local scale. Studying landfill microbiomes could therefore help to define the Anthropocene and reveal its consequences.