Gram-positive-staining, anaerobic, non-spore-forming, lactate- and acetate-producing bacterial strains were isolated from the digestive tracts of different bumblebee species (Bombus lucorum, Bombus pascuorum and Bombus lapidarius). All of the isolates produced fructose-6-phosphate phosphoketolase activity. A representative strain, BluCI/TP^T, was characterized further. Cells of strain BluCI/TP^T showed occasional bifurcation and irregular constrictions. The bacterium utilized a wide range of carbohydrates. Glucose was fermented to acetate and lactate. The DNA base composition was 47.2 mol% G+C. Complete 16S rRNA and partial hsp60 gene sequences were obtained and phylogenetic relationships were determined. Strain BluCI/TP^T and related isolates were located in the actinobacterial cluster and were closely related to the genera Bifidobacterium, Scardovia, Aeriscardovia and Parascardovia. The results presented support the proposal of a novel species to accommodate strain BluCI/TP^T, with the name Bifidobacterium bombi sp. nov.; the type strain is BluCI/TP^T (=DSM 19703^T =ATCC BAA-1567^T).