A Gram-stain-negative, non-flagellated, gliding, rod-shaped bacterial strain, designated WT-MY15(T), was isolated from wood falls in the South Sea in Korea and subjected to a polyphasic taxonomic study. Strain WT-MY15(T) grew optimally at pH 7.0-8.0, at 25 °C and in the presence of 2.0 % (w/v) NaCl. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain WT-MY15(T) clustered with the type strains of two Olleya species, exhibiting 16S rRNA gene sequence similarity values of 97.7-98.1 %. Strain WT-MY15(T) contained MK-6 as the predominant menaquinone. The fatty acid and polar lipid profiles of strain WT-MY15(T) were similar to those of Olleya aquimaris L-4(T) and Olleya marilimosa CIP 108537(T). The DNA G+C content of strain WT-MY15(T) was 42.8 mol% and its mean DNA-DNA relatedness values with O. aquimaris L-4(T) and O. marilimosa CIP 108537(T) were 8.3 and 5.6 %, respectively. The phylogenetic and genetic distinctiveness and differential phenotypic properties revealed that strain WT-MY15(T) is separate from the two recognized species of the genus Olleya. On the basis of the data presented, strain WT-MY15(T) is considered to represent a novel species of the genus Olleya, for which the name Olleya namhaensis sp. nov. is proposed. The type strain is WT-MY15(T) ( = KCTC 23673(T) = CCUG 61507(T)). An emended description of the genus Olleya is also presented.