A total of 32 suspected Pasteurellaceae strains isolated from polar and brown bears were characterized by genotypic and phenotypic tests. Phylogenetic analysis of partial 16S rRNA and rpoB gene sequences showed that the isolates investigated formed two closely related monophyletic groups. Based on 16S rRNA gene sequence comparison Bibersteinia trehalosi was the closest related validly published species, with 95.4 % similarity to the polar bear group and 94.4 % similarity to the brown bear group. Otariodibacter oris was the closest related species based on rpoB sequence comparison with an rpoB similarity at 89.8% with the polar bear group and 90% similarity with the brown bear group. Members of the bear genera could be separated from existing genera of the Pasteurellaceae by three to ten phenotypic characters and the two novel species could be separated from each other by two phenotypic characters. The DNA G+C content of strain Pb43106T is 39.3 mol%.It is proposed that the strains should be classified as representatives a new genus, Ursidibacter gen. nov., with two new species U. maritimus sp. nov. isolated from polar bears with the type strain Pb43106T (=CCUG 65144T =DSM 28137T)and U. arcticus sp. nov. isolated from brown bears with the type strain Bamse61T (=CCUG 65145 =DSM 28138 T). The type species is Ursidibacter maritimus and the type strain Pb43106T was isolated from the oral cavity of a wild polar bear in Greenland in 2011.