Two heterotrophic, aerobic, Gram-negative, pigmented and non-motile marine bacteria that were isolated from the green alga Ulva fenestrata were studied by polyphasic taxonomic methods. 16S rDNA sequence analysis indicated that strain KMM 3912T formed a distinct lineage within the family Flavobacteriaceae. On the basis of phenotypic, chemotaxonomic, genotypic and phylogenetic analyses, the novel bacteria were classified as Ulvibacter litoralis gen. nov., sp. nov. The type strain is KMM 3912T (=KCTC 12104T=CCUG 47093T).