A taxonomic study was performed on strain QM42(T), which was isolated from coastal seawater from an aquaculture site near Qingdao, China. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain QM42(T) was a member of the class Gammaproteobacteria. Cells of strain QM42(T) were Gram-negative, yellow, aerobic and rod-shaped. The strain formed a distinct phyletic line with less than 91 % 16S rRNA gene sequence similarity to its closest relatives with validly published names within the class Gammaproteobacteria. The genomic DNA G+C content was 51.9 mol%. The major fatty acids were C(16 : 1)omega7c/iso-C(15 : 0) 2-OH, C(18 : 1)omega7c and C(16 : 0). Based on data from a polyphasic chemotaxonomic, physiological and biochemical study, strain QM42(T) is considered to represent a novel genus and species, for which the name Gilvimarinus chinensis gen. nov., sp. nov., is proposed. The type strain is QM42(T) (=CGMCC 1.7008(T)=DSM 19667(T)).