A Gram-negative, non-motile bacterium, designated KSL5401-037$^T$, was isolated from a sewage treatment plant in Gwangju in the Republic of Korea and was characterized using a polyphasic taxonomic approach. Comparative 16S rRNA gene sequence analysis showed that strain KSL5401-037$^T$ belonged to the genus Acinetobacter in the family Moraxellaceae of the Gammaproteobacteria (Brisou and Prevot, 1954). According to a 16S rRNA gene sequence analysis, it was closely related to Acinetobacter johnsonii ATCC 17909$^T$ (97.3%), A. bouvetii 4B02$^T$ (97.2%), and A. beijerinckii 58a$^T$ (96.8%). Chemotaxonomic data revealed that strain KSL5401-037$^T$ possesses an ubiquinone system with Q-8 as the predominant compound and $C_{16:0}$ (19.2%), $C_{18:1}{omega}9c$ (19.5%), and summed feature 3 ($C_{16:1}{omega}6c$ / $C_{16:1}{omega}7c$, 34.1%) as the predominant cellular fatty acids. The major polar lipids detected in strain KSL5401-037$^T$ were diphosphatidylglycerol (DPG) and, phosphatidylethanolamine (PE), followed by phosphatidylglycerol (PG) and moderate amounts of phosphatidylcholine and phosphatidylserine. The G+C content of the genomic DNA was 41.2-42.1 mol%. Strain KSL5401-037$^T$ exhibited relatively low levels of DNA-DNA relatedness with respect to A. johnsonii DSM 6963$^T$ (17.7%) and A. bouvetii 4B02$^T$ (9.3%). The DNA-DNA relatedness values, biochemical, and physiological characteristics of strain KSL5401-037$^T$ strongly support its genotypic and phenotypic differentiation from other recognized type strains of the genus Acinetobacter. Based on these data, strain KSL5401-037T (JCM 17071$^T$ =KEMC 5401-037$^T$) should be classified in the genus Acinetobacter as a type strain of novel species, for which the name Acinetobacter kyonggiensis sp. nov. is proposed.