A thermotolerant, extremely halophilic archaeon, BC12-B1(T), was isolated from a salt mine in Baicheng county, Xinjiang province, China. Colonies were off-white-grey. The cells stained Gram-negative, were motile and irregularly long-rod-shaped (variation in both width and length) with abundant gas vesicles. The strain was able to grow at 20-55 °C (optimum, 48 °C), at pH 6.0-8.0 (optimum, 7.0-7.3), with 1.8-6.0 M NaCl (optimum, 3.0-3.5 M) and with 0.02-2.2 M Mg(2+) (optimum, 0.1-0.2 M). Cells lysed in distilled water and the minimal NaCl concentration to prevent cell lysis was 8 % (w/v). Phylogenetic analysis based on the 16S rRNA gene sequences showed that strain BC12-B1(T) was most closely related to Halopelagius inordinatus RO5-2(T) (98.5 %) with less than 95 % sequence similarity to other described species. The genomic DNA G+C content of strain BC12-B1(T) was 64.0 mol%. The DNA-DNA hybridization value between strain BC12-B1(T) and Hpl. inordinatus RO5-2(T) was 43.6 %. The major polar lipids of strain BC12-B1(T) were phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, four glycolipids and an unknown lipid. Based on phenotypic, chemotaxonomic and genotypic characteristics, strain BC12-B1(T) represents a novel species of the genus Halopelagius, for which the name Halopelagius longus sp. nov. is proposed. The type strain is BC12-B1(T) ( = CGMCC 1.12397(T) = JCM 18758(T)). An emended description of the genus Halopelagius is also provided.