A Gram-negative, rod-shaped, non-spore-forming bacterium (TR6-01(T)) was isolated from compost near Daejeon city in South Korea. On the basis of 16S rRNA gene sequence similarity, strain TR6-01(T) 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 TR6-01(T) to the genus Stenotrophomonas. The results of DNA-DNA hybridization and physiological and biochemical tests allowed genotypic and phenotypic differentiation of strain TR6-01(T) from the five Stenotrophomonas species with validly published names. TR6-01(T) therefore represents a novel species, for which the name Stenotrophomonas koreensis sp. nov. is proposed, with the type strain TR6-01(T) (= KCTC 12211(T) = JCM 13256(T)).