An obligate anaerobic, Gram-reaction-negative, non-sporeforming, non-motile, rod shaped bacterium designated YMC B3181T was isolated from the blood of a patient with peritonitis. Strain B3181T grew at 20 to 40°C with optimum growth at 37°C. 16S rRNA gene sequence similarity showed strain B3181T belongs to the genus Parabacteroides and is closely related to Parabacteroides faecis 157T (97.3%), Parabacteroides gordonii MS-1T (96.6%), and Parabacteroides goldsteinii DSM 19448T (95.7%). The G + C content of the genomic DNA was 42.3 mol%. The major cellular fatty acids were anteiso- C15:0 and iso-C17:0 3-OH, and the predominant respiratory quinones were MK-9 and MK-10 menaquinones. Genomic and chemotaxonomic data supported affiliation of B3181T with the genus Parabacteroides. Strain B3181T was phylogenetically and phenotypically different from recognized species of the genus Parabacteroides. Accordingly, this isolate belongs to a novel species for which the name Parabacteroides chongii sp. nov. (type strain YMC B3181T = LMG 30065T = KACC 19034T) is proposed.