A Gram-negative, aerobic and halophilic bacterium designated strain mano18T was isolated from a tidal flat area of Dae-Chun, Chung-Nam, Korea. This strain was motile by means of polar flagella, occasionally forming rosette-like aggregates, reduced nitrate to nitrite, required sodium ions for growth, exhibited catalase and oxidase activities and contained Q-10 as the major quinone and C(18 : 1)omega7c as the dominant cellular fatty acid. Analysis of the 16S rRNA gene sequence revealed that this strain is affiliated with a cluster within the Alphaproteobacteria. Strain mano18T synthesized bacteriochlorophyll under aerobic conditions. The 16S rRNA gene sequence similarity between strain mano18T and the most closely related species, Stappia aggregata DSM 13394T, was 98.5 %. Levels of DNA-DNA relatedness between strain mano18T and the type strains of S. aggregata and Stappia stellulata were respectively 6.2-11.2 and 3.3-7.6 %. Strain mano18T, like other Stappia strains, possesses carbon monoxide dehydrogenase genes. The results of DNA-DNA hybridization and the polyphasic data confirmed that strain mano18T can be considered to represent a novel taxon in the genus Stappia. The name Stappia marina sp. nov. is proposed for the tidal flat isolate; the type strain is strain mano18T (= KCTC 12288T = DSM 17023T).