In this study, we classified the five strains (ChDC F128(T), ChDC F145, ChDC F174, ChDC F206, and ChDC F300) as a novel species of genus Fusobacterium by DNA-DNA hybridization and multi-locus phylogenetic analysis (MLPA), based on a single sequence (24,715 bp) of 22 concatenated housekeeping genes, with morphological and chemotaxonomic characteristics. DNA-DNA hybridization data showed that the values of genomic relatedness between ChDC F128(T) and each of the other novel strains were ranged from 79.0 to 82.6 %, while those of genomic relatedness between ChDC F128(T) and type strain of each of subspecies of F. nucleatum or Fusobacterium periodonticum were ranged from 40.9 to 54.4 %. MLPA revealed that the 5 strains were clustered as one group and clearly discriminated with F. nucleatum and F. periodonticum with 100 % bootstrap value. The DNA G+C content of the five novel strains were ranged from 26.9 to 27.0 mol%. The cellular fatty acid analysis of clinical isolates and type strains revealed C-14:0, C-16:0, and cis-9 C-16:1 as the major fatty acids. The cell wall peptidoglycan of the 5 strains was comprised of meso-lanthionine. These results show that the 5 strains are novel species and belong to the genus Fusobacterium. Strain ChDC F128(T) (=KCOM 1249(T) = KCTC 5108(T) = JCM 30218(T)) is suggested to be the type strain of a novel species of genus Fusobacterium, for which the name Fusobacterium hwasookii sp. nov. is proposed.