Osteodiscus cascadiae or 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 in occurs at depths of from 1,900 to 3,000 metres (6,200 to 9,800 ft). It grows to a lengths from 7.4 centimetres (2.9 in) SL (male/unsexed) to 8.5 centimetres (3.3 in) 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.