A Gram-stain negative, strictly aerobic, mesophilic bacterial strain, designated strain S23T, was isolated from pond-side soil of an artificial pond in South Korea. Cells were observed to be peritrichously flagellated short rods showing positive oxidase and catalase activities. Growth of strain S23T was observed at 15–37 °C (optimum, 30 °C), pH 5.0–9.0 (optimum, pH 7.0–8.0) and 0–2% (w/v) NaCl (optimum, 0–0.5%). The major respiratory quinone was identified as ubiquinone-8 and the major fatty acids were identified as C16:0, cyclo-C17:0, summed feature 3 (C16:1ω7c and/or C16:1ω6c) and summed feature 8 (C18:1ω7c and/or C18:1ω6c). The G + C content of the genomic DNA was determined to be 65.1 mol%. Phosphatidylglycerol, phosphatidylethanolamine and an unidentified phospholipid were detected as the major polar lipids. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain S23T formed a phyletic lineage with Cupriavidus necator N-1T within the genus Cupriavidus. Strain S23T is closely related to C. necator N-1T (99.2%), Cupriavidus basilensis DSM 11853T (98.8%), Cupriavidus alkaliphilus ASC-732T (98.8%) and Cupriavidus numazuensis TE26T (98.7%), based on 16S rRNA gene sequence similarities. However, the DNA–DNA relatedness values between strain S23T and the closely related type strains were less than 46%. On the basis of phenotypic, chemotaxonomic and molecular properties, strain S23T represents a novel species of the genus Cupriavidus, for which the name Cupriavidus lacunae sp. nov. is proposed. The type strain is S23T (KACC 19624T = JCM 32674T).