Deltaproteobacteria are a ubiquitous class of bacteria that play a substantial role in carbon and nutrient cycling. However, our understanding of Deltaproteobacteria is biased towards cultured exemplars. To better understand the biodiversity and ecology of the Deltaproteobacteria, we obtained hundreds of unique, uncultured metagenome-assembled genomes (MAGs) from a variety of coastal and deep-sea sediments. These 402 Deltaproteobacteria MAGs represent a 28% increase in Deltaproteobacteria genomes. Phylogenomic analyses revealed 12 novel lineages which consist entirely of uncultured representatives. Among these are two lineages that appear to represent a new order, which are capable of denitrification and dissimilatory nitrate reduction to ammonia (DNRA). Metabolic inference of Deltaproteobacteria MAGs reveals extensive versatility, central carbon metabolism, and a broad distribution of the Wood-Ljungdahl pathway for CO2 fixation. 54% of Deltaproteobacteria MAGs encode dissimilatory sulfite reductases (DsrAB), and for those with the ability to reduce sulfate, several dsr genes are related to those from thermophiles. This study expands the genetic catalog of Deltaproteobacteria and provides a better ecological context for Deltaproteobacteria worldwide. The description of these new lineages highlights that there is much to be learned about this globally distributed proteobacteria