A novel Gram-stain-negative, coccus to oval-shaped, non-motile bacterium, designated strain S5T, was isolated from lagoon sediments collected from North Carolina, USA. Strain S5T was able to grow at 12-45 °C (optima, 30-37 °C) and at pH 6.3-9.0 (optima, 6.5-7.5). No added NaCl was required for growth of strain S5T. Strain S5T was positive for catalase and oxidase activity. C18 : 1ω6c/C18 : 1ω7c, C16 : 1ω6c/C16 : 1ω7c and C16 : 0 were predominant fatty acids with minor amounts of C8 : 0 3-OH, C14 : 0, C16 : 0 3-OH, C18 : 1 2-OH, C14 : 1ω5c, C16 : 1ω5c and C19 : 0 cyclo ω8c. Diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and an unidentified glycolipid were major polar lipids. Minor amounts of an unidentified amino lipid and three unidentified lipids were also detected. The G+C content of the genomic DNA was 73.5 mol%. 16S rRNA gene sequence comparisons indicated that strain S5T represents a member of the genus Roseomonas within the family Acetobacteraceae of the class Alphaproteobacteria. Strain S5T had a sequence similarity of 97.80 % with Roseomonas rhizosphaerae YW11T, 97.69 % with Roseomonas aestuarii JC17T and <97 % with other members of the genus Roseomonas. However, strain S5T showed only 45.2±2 and 17±2 % relatedness (based on DNA-DNA hybridization) with R. rhizosphaerae KACC 17225T (=YW11T) and R. aestuarii KCTC 22692T (=JC17T), respectively. Distinct morphological, physiological and genotypic differences from previously described taxa support the classification of strain S5T as a representative of a novel species in the genus Roseomonas, for which the name Roseomonas rubra sp. nov. is proposed. The type strain is S5T (=KEMB 563-468T=JCM 31177T).