This review provides an overview of the anaerobic oxidation of methane (AOM) and the key microorganisms involved, particularly the anaerobic methanotrophic archaea (ANME). AOM is a crucial process in controlling global methane budgets, as it consumes about 85% of the annual global methane production and 60% of its consumption. The review highlights the significance of AOM in global methane budgets, the history of AOM research, and the geochemical signatures, rates, and environmental controls of AOM. It also discusses the diversity, structure, and morphology of ANME populations, their bacterial partners, and the habitats where they are found. The review further explores the physiology of AOM consortia, including stoichiometry, intermediates, kinetics, and energy yield. Additionally, it examines the functional genes, genomics, and proteomics of AOM, including the role of methyl-coenzyme M reductase (MCR) and the mcrA gene. The review concludes by discussing the potential for AOM to be coupled to electron acceptors other than sulfate and the challenges in understanding the biochemical coupling of growth to low-energy processes like AOM.This review provides an overview of the anaerobic oxidation of methane (AOM) and the key microorganisms involved, particularly the anaerobic methanotrophic archaea (ANME). AOM is a crucial process in controlling global methane budgets, as it consumes about 85% of the annual global methane production and 60% of its consumption. The review highlights the significance of AOM in global methane budgets, the history of AOM research, and the geochemical signatures, rates, and environmental controls of AOM. It also discusses the diversity, structure, and morphology of ANME populations, their bacterial partners, and the habitats where they are found. The review further explores the physiology of AOM consortia, including stoichiometry, intermediates, kinetics, and energy yield. Additionally, it examines the functional genes, genomics, and proteomics of AOM, including the role of methyl-coenzyme M reductase (MCR) and the mcrA gene. The review concludes by discussing the potential for AOM to be coupled to electron acceptors other than sulfate and the challenges in understanding the biochemical coupling of growth to low-energy processes like AOM.