Two Gram-stain-negative, rod-shaped, orange, catalase- and oxidase-positive, non-motile bacteria, designated W13M1A(T) and W15M10(T), were isolated from the marine sponges Suberites carnosus and Leucosolenia sp., respectively, which were sampled from Lough Hyne, Co. Cork, Ireland. Analysis of the 16S rRNA gene sequences of these isolates revealed that they are members of the genus Maribacter, in the family Flavobacteriaceae of the phylum Bacteroidetes. The type strain most closely related to strain W13M1A(T) is Maribacter forsetii DSM 18668(T) with a gene sequence similarity of 96.5%. The closest related type strain to strain W15M10(T). is Maribacter orientalis DSM 16471(T) With a gene sequence similarity of 98.3%. Phylogenetic inference and phenotypic data combined indicate that the isolates represent two novel species of the genus Maribacter, for which the names Maribacter spongiicola sp. nov. with type strain W15M10(T) (=NCIMB 14725(T)=DSM 25233(T)) and Maribacter vaceletii sp. nov. with type strain W13M1A(T) (=NCIMB 14724(T)=DSM 25230(T)), are proposed.