A Gram-negative, yellow-pigmented bacterium capable of gliding motility, designated strain WPCB118(T), was isolated from fresh water collected from the Woopo wetland (Republic of Korea). Cells were rod-shaped and sometimes filamentous. The major fatty acids were iso-C(15 : 0) 2-OH and/or C(16 : 1)omega7c (45.6 %), C(16 : 1)omega5c (18.5 %), iso-C(15 : 0) (9.5 %) and C(16 : 0) (8.8 %). The predominant menaquinone and polar lipid were MK-7 and phosphatidylethanolamine, respectively. The DNA G+C content was 53.3 mol%. A phylogenetic tree based on 16S rRNA gene sequences showed that strain WPCB118(T) had an evolutionary lineage within the radiation encompassing the members of the family 'Flexibacteraceae', its closest neighbour being Spirosoma linguale LMG 10896(T) (93.7 % gene sequence similarity). Data from this polyphasic study indicated that strain WPCB118(T) could not be assigned to any recognized species. Strain WPCB118(T) represents a novel species of the genus Spirosoma, for which the name Spirosoma rigui sp. nov. is proposed. The type strain is WPCB118(T) (=KCTC 12531(T)=NBRC 101117(T)).