The giant catfish species (Pangasianodon gigas) is the world's largest freshwater fish. This species, which inhabits Southeast Asia's Mekong River, has been listed as critically endangered on the 2003 IUCN Red List of Threatened Species. Find out more about this fish and the threats that now face it in National Geographic's article, Giant Catfish Critically Endangered. You can also view pictures of the giant catfish in the Giant Catfish photo gallery.