A Gram-negative, rod-shaped, non-spore-forming bacterium (TR6-01T) was isolated from compost near Daejeon city in South Korea. On the basis of 16S rRNA gene sequence similarity, strain TR6-01T was shown to belong to the class Gammaproteobacteria, related to Stenotrophomonas acidaminiphila (97.1 %) and Stenotrophomonas maltophilia (96.9 %); the phylogenetic distance from any other established species within the genus Stenotrophomonas was less than 97.0 %. Phenotypic and chemotaxonomic data (major ubiquinone Q-8; fatty acid profile) supported the affiliation of strain TR6-01T to the genus Stenotrophomonas. The results of DNA-DNA hybridization and physiological and biochemical tests allowed genotypic and phenotypic differentiation of strain TR6-01T from the five Stenotrophomonas species with validly published names. TR6-01T therefore represents a novel species, for which the name Stenotrophomonas koreensis sp. nov. is proposed, with the type strain TR6-01T (= KCTC 12211T = JCM 13256T).