A Streptomyces strain isolated from a mangrove sediment was classified using a polyphasic approach. The organism, isolate GY1(T), was found to have chemical and morphological properties typical of members of the genus Streptomyces. The isolate was shown to form a distinct phyletic line within the Streptomyces radiopugnans 16S rRNA gene subclade and to be closely related to the type strain of Streptomyces fenhuangensis (98.7 % similarity). It is also closely related to the type strain of Streptomyces bakulensis which was also closely related to members of the Streptomyces glaucosporus 16S rRNA gene subclade. Isolate GY1(T) was distinguished readily from the S. barkulensis type strain and from species classified in the S. radiopugnans clade using a combination of morphological and physiological properties, including a requirement for seawater for growth. Based on the genotypic and phenotypic data, it is proposed that isolate GY1(T) (=NCIMB 14980(T), NRRL B-69296(T)) be classified in the genus Streptomyces as Streptomyces mangrovi sp. nov.