Cetomimidae is a family of small, deep-sea cetomimiform fish. They are among the most deep-living fish known, with some species recorded at depths in excess of 3,500 m (11,500 ft). Females are known as flabby whalefishes, Males are known as bignose fishes, while juveniles are known as tapetails and were formerly thought to be in a separate family, dubbed Mirapinnidae. Adults exhibit extreme sexual dimorphism, and the adult males were once thought to be exemplars of still another family, Megalomycteridae.

Thought to have a circumglobal distribution throughout the Southern Hemisphere, Cetomimidae are the most diverse family of whalefishes. The largest species, Gyrinomimus grahami, reaches a length of some 40 cm. They are distinguished from other whalefishes by their loose, scaleless skin and lack of photophores.