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Gram-stain-negative, strictly aerobic, non-spore-forming, non-motile, and rod-shaped bacterial strains, designated NC18^T and NC20, were isolated from the sediment near-vertical borehole effluent originating 714 m below the subsurface located in the Soudan Iron Mine in Minnesota, USA. The 16S rRNA gene sequence showed that strains NC18^T and NC20 grouped with members of the genus <i>Martelella</i>, including <i>M. mediterranea</i> DSM 17316^T and <i>M. limonii</i> YC7034^T. The genome sizes and G + C content of both NC18^T and NC20 were 6.1 Mb and 61.8 mol%, respectively. Average nucleotide identity (ANI), the average amino acid identity (AAI), and digital DNA–DNA hybridization (dDDH) values were below the species delineation threshold. Pan-genomic analysis showed that NC18^T, NC20, <i>M. mediterranea</i> DSM 17316^T, <i>M. endophytica</i> YC6887^T, and <i>M. lutilitoris</i> GH2-6^T had 8470 pan-genome orthologous groups (POGs) in total. Five <i>Martelella</i> strains shared 2258 POG core, which were mainly associated with amino acid transport and metabolism, general function prediction only, carbohydrate transport and metabolism, translation, ribosomal structure and biogenesis, and transcription. The two novel strains had major fatty acids (>5%) including summed feature 8 (C18:1 ω7c and/or C18:1 ω6c), C19:0 cyclo ω8c, C16:0, C18:1 ω7c 11-methyl, C18:0, and summed feature 2 (C12:0 aldehyde and/or iso-C16:1 I and/or C14:0 3-OH). The sole respiratory quinone was uniquinone-10 (Q-10). On the basis of polyphasic taxonomic analyses, strains NC18^T and NC20 represent novel species of the genus <i>Martelella</i>, for which the name <i>Martelella soudanensis</i> sp. nov. is proposed. The type strain is NC18^T (=KTCT 82174^T = NBRC 114661^T).