Three rod-shaped, Gram-negative, chemo-organotrophic, heterotrophic, strictly aerobic, gliding bacterial strains, KT02ds18-4, KT02ds18-5 and KT02ds18-6T, were isolated from North Sea surface waters near the island of Helgoland, Germany. Their taxonomic position was investigated by a polyphasic approach. The three strains were light yellow, oxidase- and catalase-positive, and grew optimally at 25 degrees C, at pH 7.5, and in the presence of 2.5 % (w/v) NaCl. The Chargaff's coefficient was 34.2-34.4 mol%. The three strains shared >90 % DNA-DNA relatedness and an identical 16S rRNA gene sequence. Comparative 16S rRNA gene sequence analysis allocated the three strains to the genus Maribacter in the family Flavobacteriaceae, with similarities of 97.0-97.4 % to five of the recognized Maribacter species. Their low level of DNA-DNA relatedness (<20 %) with these species and differentiating phenotypic characteristics demonstrated that they constitute a new Maribacter species for which the name Maribacter forsetii sp. nov. is proposed. Strain KT02ds18-6T (=CIP 109504T=DSM 18668T) is the type strain. An emended description of the genus Maribacter is also proposed.