In Japan, during a screening of lactic acid bacteria in spent mushroom substrates, an unknown bacterium was isolated and could not be assigned to any known species. Strain YK48GT is Gram-stain-positive, rod-shaped, non-motile, non-spore-forming and catalase-negative. The isolate grew in 0–4 % (w/v) NaCl, at 15–37 °C (optimum, 30 °C) and at pH 4.0–8.0 (optimum, pH 6.0). The genomic DNA G+C content of strain YK48GT was 42.5 mol%. Based on its 16S rRNA gene sequence, strain YK48GT represented a member of the genus Lentilactobacillus and showed the highest pairwise similarity to Lentilactobacillus rapi DSM 19907T (97.86 %). Phylogenetic analyses based on amino acid sequences of 466 shared protein-encoding genes also revealed that the strain was phylogenetically positioned in the genus Lentilactobacillus but did not suggest an affiliation with previously described species. The average nucleotide identity and digital DNA–DNA hybridization values between strain YK48GT and the type strains of phylogenetically related species were 72.2–76.6% and 19.0–21.2 %, respectively, indicating that strain YK48GT represents a novel species within the genus Lentilactobacillus . Phenotypic data further confirmed the differentiation of strain YK48GT from other members of the genus Lentilactobacillus . According to the results of the polyphasic characterization presented in this study, strain YK48GT represents a novel species of the genus Lentilactobacillus , for which the name Lentilactobacillus fungorum sp. nov. is proposed. The type strain is YK48GT (=JCM 32598T=DSM 107968T).