Bythaelurus bachi, commonly known as Bach's catshark, is a species of shark belonging to the family Pentanchidae, the deepwater catsharks. This shark is found on the southern Madagascar Ridge in the southwestern Indian Ocean.[1] This stout-bodied catshark is thought to inhabit the deep sea at depths of .
Compared to all of its congeners in Western Indian Ocean, Bach's catshark has higher diversity of dermal denticle morphology in general, lighter body coloration, and the presence of numerous partially composite papillae on its tongue and palate (the roof of a mouth).