Ompok is a genus of Old World catfishes in the family Siluridae -- the sheatfishes, which also includes the giant Wallago and the translucent glass catfishes of the genus Kryptopterus. Ompok is distributed across South and Southeast Asia, with the atlas's records spanning Indonesia, Malaysia, India, Bangladesh, Myanmar, Pakistan, Sri Lanka, and Afghanistan. Species share the family's characteristic body plan: a laterally compressed, scaleless body, a long anal fin, and a small or absent adipose fin, typically living in rivers, floodplains, and slow-moving lowland waters. The common names in circulation -- butter catfish and glass catfish -- reflect both the smooth, silvery flesh prized as food and the pale, semi-translucent look of several species. The atlas covers 21 species with an unusually wide size range, from around 3 in up to 20 in in the largest forms.
Ompok is of considerably more importance as a food fish than as an aquarium subject. Species such as Ompok bimaculatus (the two-spot glass catfish, widely sold as butter catfish) and O. pabda (pabda catfish) support significant inland fisheries and aquaculture across South Asia, and pressure from fishing and habitat loss appears to be catching up with a number of species in the genus: the atlas's tally shows a meaningful share rated Vulnerable, Near Threatened, or Endangered rather than comfortably Least Concern. A few species do circulate in the ornamental trade as oddball glass catfish, but Ompok is best understood as a genus of primarily scientific and food-fishery interest rather than a hobby mainstay.