A Gram-staining-negative, non-motile, strictly aerobic bacterium, strain X12M-4T, was isolated from Xiaochaidan Lake, a salt lake (salinity 9.9 %, w/w) in Qaidam basin, Qinghai Province, China. Its taxonomic position was determined by using a polyphasic approach. Strain X12M-4T was catalase- and oxidase-positive. Cells were rod-shaped, 0.5–0.8 μm wide and 1.1–1.6 μm long. Growth was observed in the presence of 0–11.0 % (w/v) NaCl (optimum, 5.0–6.0 %) and at 15–40 °C (optimum, 25 °C) and pH 6.5–9.5 (optimum, pH 7.0). No growth occurred at 10 °C or 45 °C. Strain X12M-4T contained C18 : 1ω7c, C19 : 0 cyclo ω8c and C16 : 0 as the major fatty acids (>10.0 %). The predominant respiratory quinone was Q-10.The major polar lipids were phosphatidylcholine, phosphatidylglycerol, diphosphatidglycerol, an unknown aminolipid and an unidentified lipid. The DNA G+C content was 65.7 mol% (determined using T m). Strain X12M-4T showed highest 16S rRNA gene sequence similarities to Maritimibacter alkaliphilus HTCC2654T (96.7 %), Roseibacterium elongatum DSM 19469T (96.4 %), Tropicimonas aquimaris DPG-21T (95.6 %), ‘Roseibacterium beibuensis’ JLT1202r (95.6 %) and Tropicimonas sediminicola M97T (95.5 %) and < 95.5 % to others. Phylogenetic trees based on 16S rRNA gene sequences indicated that strain X12M-4T formed a robust cluster with M. alkaliphilus HTCC2654T. On the basis of the data, it is concluded that strain X12M-4T represents a novel species of the genus Maritimibacter, for which the name Maritimibacter lacisalsi sp. nov. is proposed. The type strain is X12M-4T ( = CGMCC 1.12922T = JCM 30555T). To accommodate the novel species, the description of the genus Maritimibacter was emended.