A Gram-strain-negative, strictly aerobic, rod-shaped, catalase-positive, oxidase-positive and pinkish beige colony-forming bacterial strain designated as BMJM1T was isolated from a marine sample collected from coastal water near Tongyeong, Republic of Korea. The results of phylogenetic analysis based on 16S rRNA gene sequences indicated that BMJM1T represents a member of the genus Leisingera as it is closely related to Leisingera daeponensis KCTC 12794T (98.27%), Leisingera caerulea DSM 24564T (97.98%), Leisingera aquaemixtae KCTC 32538T (97.91%), Leisingera methylohalidivorans DSM 14336T (97.26%) and Leisingera aquimarina DSM 24565T (97.25%). Optimal growth occurred at 25-30°C, pH 7.0 and with 2% NaCl. Digital DNA-DNA hybridisation (dDDH) and average nucleotide identity (ANI) values between strain BMJM1T and the closely related species of the genus Leisingera were below 40 and 90%, respectively, which are far below the thresholds to delineate a novel species. The predominant fatty acids (>10%) are summed feature 8 (C18:1ω7c and/or C18:1ω6c) (68.4%) and C14:1iso E (11.6%). The major polar lipids were phosphatidylethanolamine and phospholipid. The major isoprenoid quinone was ubiquinone-10. The DNA G+C content was 64.0%. On the basis of the results of the polyphasic taxonomic characterisation, BMJM1T represents a novel species of the genus Leisingera, for which the name is Leisingera thetidis sp. nov. is proposed, with that type strain BMJM1T (= KCTC 92110T = GDMCC 1.2992T).