Bacterial strain YP382-1-AT was isolated from marine sediment at Gimnyeong Beach, Jeju Island, Republic of Korea. This strain was found to be aerobic and Gram-stain-negative, with red to purple pigmentation. Cells of strain YP382-1-AT were motile, had a single polar flagellum and were short rod-shaped. The predominant quinone in strain YP382-1-AT was Q-10. The major fatty acid was C18 : 1ω7c and the DNA G+C content was 60.3 mol%. Phylogenetic analysis based on comparisons of 16S rRNA gene sequences showed that strain YP382-1-AT belonged to the order Rhizobiales in the class Alphaproteobacteria. This strain exhibited very low 16S rRNA gene sequence similarity (no higher than 94.5 %) to the type strains of recognized bacterial species of the order Rhizobiales. Strain YP382-1-AT appeared as a distinct branch within Rhizobiales in the phylogenetic tree generated. On the basis of the data presented, strain YP382-1-AT is considered to represent a novel species of a new genus, classified within a new family. The name Mabikibacter ruber gen. nov., sp. nov., of the new family Mabikibacteraceae fam. nov. is proposed. The type strain of Mabikibacter ruber is YP382-1-AT (=JCM 31727T=KCCM 90265T).