Four marine bacterial strains were isolated from a thallus of the brown alga Ascophyllum nodosum collected in Roscoff, France. Cells were Gram-stain-negative, strictly aerobic, non-flagellated, gliding, rod-shaped and grew optimally at 25–30 °C, at pH 7–8 and with 2–4 % NaCl. Phylogenetic analyses of their 16S rRNA gene sequences showed that the bacteria were affiliated to the genus Zobellia (family Flavobacteriaceae , phylum Bacteroidetes ). The four strains exhibited 97.8–100 % 16S rRNA gene sequence similarity values among themselves, 97.9–99.1 % to the type strains of Zobellia amurskyensis KMM 3526^T and Zobellia laminariae KMM 3676^T, and less than 99 % to other species of the genus Zobellia . The DNA G+C content of the four strains ranged from 36.7 to 37.7 mol%. Average nucleotide identity and digital DNA–DNA hybridization calculations between the new strains and other members of the genus Zobellia resulted in values of 76.4–88.9 % and below 38.5 %, respectively. Phenotypic, phylogenetic and genomic analyses showed that the four strains are distinct from species of the genus Zobellia with validly published names. They represent two novel species of the genus Zobellia , for which the names Zobellia roscoffensis sp. nov. and Zobellia nedashkovskayae sp. nov. are proposed with Asnod1-F08^T (RCC6906^T=KMM 6823^T=CIP 111902^T) and Asnod2-B07-B^T (RCC6908^T=KMM 6825^T=CIP 111904^T), respectively, as the type strains.