Osteodiscus cascadiae, the bigtail snailfish, is a marine fish in the family Liparidae (snailfishes or seasnails). This species is known from the deep waters of the Northeast Pacific (British Columbia, Canada to at least Oregon, United States) where it occurs at depths of 1900mto3000mm (6,200feetto10,000feetm). It grows to length from 7.4cm (02.9inches) SL (male/unsexed) to 8.5cm (03.3inches) SL (female). This species is one of three known members of its genus. The species name cascadiae refers to the Cascadia Abyssal Plain, a location off Oregon where the fish has been found.