A novel Gram-negative, rod-shaped and motile bacterial strain, designated strain M36T, was isolated from a culture of a bloom-forming cyanobacterium, Microcystis sp., collected from a eutrophic lake in Korea. Its taxonomic position was investigated by using a polyphasic taxonomic approach. The isolate was found to grow aerobically at 15–42 °C (optimum 25 °C), pH 7.0–11.0 (optimum pH 8.0) and in the presence of 0–1.0% (w/v) NaCl (optimum 0% NaCl) on R2A medium. The phylogenetic analysis based on 16S rRNA gene sequences revealed that the strain M36T is closely related to Acidovorax anthurii DSM 16745T (98.1%), Acidovorax konjaci DSM 7481T (97.7%) and Acidovorax avenae DSM 7227T (97.0%) and also formed a clear phylogenetic lineage with other Acidovorax species. DNA–DNA relatedness between strain M36T and the closely related species of the genus Acidovorax was <30%. The major fatty acid components identified included summed feature 3 (C16:1ω7c and/or C16:1ω6c), C16:0 and summed feature 8 (C18:0ω7c and/or C18:0ω6c). The DNA G+C content of strain M36T was determined to be 66.8 mol%. Based on above polyphasic evidence, strain M36T is concluded to represent a new species of genus Acidovorax, for which the name Acidovorax lacteus sp. nov. is proposed. The type strain is M36T (=KCTC 52220T = JCM 31890T).