The family Desulfuromonadaceae is part of the Deltaproteobacteria class in the phylum Proteobacteria and contains the genera Desulfuromonas, Desulfuromusa, Pelobacter, Malonomonas, and Geoalkalibacter. The genera Geothermobacter and Geopsychrobacter, while currently part of the closely related family Geobacteraceae, have phylogenetic and phenotypic characteristics more closely aligned with Desulfuromonadaceae and are therefore discussed in this chapter. Members of the family are strictly anaerobic, although there is some tolerance to oxygen, and found widely in anoxic environments, particularly freshwater and marine sediments. They play important roles in the degradation of organic matter and are involved in syntrophic associations especially with methanogens and phototrophic green sulfur bacteria. Most members of Desulfuromonadaceae have a respiratory metabolism; however, Pelobacter and Malonomonas are almost exclusively fermentative with the exception of Pelobacter seleniigenes which is primarily a respirer. The majority of species are mesophiles, but there are several psychrophilic, alkaliphilic/ alkalitolerant, and one thermophilic species. A wide range of substrates are metabolized by family members, ranging from organic acids to aromatic and chlorinated compounds. Sugars are used only by one out of the twenty-three species, Geothermobacter ehrlichii. The family requires some rearrangement with several species, needing reclassification to new genera. In particular, the genus Pelobacter has significant phylogenetic disparity.