A novel Gram-negative, obligately anaerobic, non-motile, non-spore forming, and rod-shaped bacterium, designated strain JS262(T), was isolated from human subgingival plaque of periodontitis lesion and was characterized by polyphasic taxonomic analysis. Comparison of 16S ribosomal RNA gene (16S rDNA) sequence revealed that the strain belonged to the genus Prevotella. The percent similarity of 16S rDNA of strain JS262(T) was closest to those of Prevotella buccae ATCC 33574(T) (89.1%) and Prevotella shahii JCM 12083(T) (88.9%). The major fatty acids of strain JS262(T) were C-16:0 (29.2%), iso-C-15:0 (19.2%), and anteiso-C-15:0 (16.9%). Complete genome of strain JS262(T) was 2,691,540bp in length and the G+C content was 43.9mol%. Average nucleotide identity and genome-to-genome distance values between strain JS262(T) and P. buccae ATCC 33574(T) or P. loescheii DSM 19665(T) were >70.4% and >30.1%, respectively. On the basis of these data, a novel Prevotella species is proposed: Prevotella koreensis sp. nov. The type strain of P. koreensis is JS262(T) (=KCOM 3155(T)=JCM 33298(T)).