Three Gram-negative, rod-shaped, non-spore-forming, nitrate-reducing isolates (R-32746, R-32768T and R-32729T) were obtained from soil. Analysis of repetitive sequence-based PCR showed that the three isolates represented two different strains. 16S rRNA gene sequence analysis and DNA–DNA hybridization placed them within the genus Stenotrophomonas and revealed that they were genotypically different from each other and from all recognized Stenotrophomonas species. Analysis of the fatty acid composition and physiological and biochemical tests allowed differentiation from their closest phylogenetic neighbours. They are therefore considered to represent two novel species, for which the names Stenotrophomonas terrae sp. nov. and Stenotrophomonas humi sp. nov. are proposed, with strains R-32768T (=LMG 23958T=DSM 18941T) and R-32729T (=LMG 23959T=DSM 18929T), respectively, as the type strains.