A gram-stain-negative and strictly aerobic bacterium, designated strain HR-E-T, was isolated from a water sample of the Han River in South Korea. Cells were catalase-negative and oxidase-positive motile rods with a flagellum. The strain grew at 10-37 degrees C and pH 7-8 and in the presence of 0-2% (w/v) NaCl. Ubiquinone-8 and summed features 3 (comprising C(16:1)7c and/or C(16:1)6c) and 8 (comprising C(18:1)7c and/or C(18:1)6c), C-16:0, iso-C-10:0 and C-12:0 3-OH were identified as the major respiratory quinone and fatty acids (>5%), respectively. The 16S rRNA gene sequence of strain HR-E-T shared the highest similarities with Perlucidibaca piscinae IMCC 1704(T) (98.1%), Perlucidibaca aquatica BK296(T) (96.8%), Paraperlucidibaca baekdonensis RL-2(T) (95.8%) and Paraperlucidibaca wandonensis WT-RY4(T) (95.7%). However, strain HR-E-T formed a phylogenetic lineage distinct from members of the family Moraxellaceae, and a taxonomic analysis by RDP Naive Bayesian rRNA Classifier classified strain HR-E-T as a new genus of the family Moraxellaceae. In addition, analyses based on rpoD, secA and gyrB gene sequences also showed that strain HR-E-T formed a lineage distinct from those of the genera Perlucidibaca and Paraperlucidibaca. Average nucleotide identity and in silico DNA-DNA hybridization values between strain HR-E-T and the type strains of P. piscinae and P. aquatica were very low with 80.1 and 23.6% and 75.7 and 21.2%, respectively. The DNA G+C content was 67.0mol%. Based on the phenotypic, genotypic and chemotaxonomic analyses, strain HR-E-T represents a novel genus of the family Moraxellaceae, for which the name Amnimonas aquatica gen. nov., sp. nov. is proposed. The type strain of the type species is HR-E-T (=KACC 19408(T)=JCM 32266(T)).