Calyptocephalella is a genus of frogs in the family Calyptocephalellidae. It is represented by a single living species, Calyptocephalella gayi, commonly known as the helmeted water toad, Chilean helmeted bull frog or wide-mouth toad. Additionally, there are a few extinct species that only are known from Late Cretaceous and Paleogene fossil remains from Patagonia in South America and in the Antarctic Peninsula . The helmeted water toad living today is aquatic to semi-aquatic, and found in deep ponds and reservoirs in central Chile and possibly adjacent west-central Argentina. This very large toad typically weighs up to 0.5–1 kg, but sometimes considerably more. It's the world's second largest frog after the Goliath frog. It is threatened by capture for human consumption, habitat loss, pollution, introduced species and the disease chytridiomycosis. It is often kept in herpetoculture; mostly locally where farmed for food, but also in other countries as a pet.