Methanohalophilus mahii is the type species of the genus Methanohalophilus, which currently comprises three distinct species with validly published names. Mhp. mahii represents moderately halophilic methanogenic archaea with a strictly methylotrophic metabolism. The type strain SLP(T) was isolated from hypersaline sediments collected from the southern arm of Great Salt Lake, Utah. Here we describe the features of this organism, together with the complete genome sequence and annotation. The 2,012,424 bp genome is a single replicon with 2032 protein-coding and 63 RNA genes and part of the Genomic Encyclopedia of Bacteria and Archaea project. A comparison of the reconstructed energy metabolism in the halophilic species Mhp. mahii with other representatives of the Methanosarcinaceae reveals some interesting differences to freshwater species.