A Gram-stain-positive, rod-shaped, non-motile, catalase-negative and facultative anaerobic strain, L88T, was isolated from suan-tsai, a traditional Taiwanese fermented mustard green. Comparative analyses of 16S rRNA, pheS and rpoA gene sequences demonstrated that strain L88Twas a member of the genus Lactobacillus. On the basis of 16S rRNA gene sequence similarity, the type strains of Lactobacillus acidifarinae (98.2 % similarity), Lactobacillus namurensis (98.1 %), Lactobacillus zymae (98.1 %) and Lactobacillus spicheri (96.8 %) were the closest neighbours to this novel strain. The average nucleotide identity, digital DNA?DNA hybridization and average amino acid identity values between L88T and its closest relatives were lower than 80, 30 and 90 %, respectively. Phenotypic and genotypic test results demonstrated that strain L88T represents a novel species of the genus Lactobacillus, for which the name Lactobacillus suantsaii sp. nov., is proposed. The type strain is L88T (=BCRC 12945T=NBRC 113535T).