The blobfish (Psychrolutes marcidus) is a deep sea fish of the family Psychrolutidae. It inhabits the deep waters off the coasts of mainland Australia and Tasmania, as well as the waters of New Zealand.

Blobfish are typically shorter than 30 cm. They live at depths between 600 and 1,200 m (2,000 and 3,900 ft) where the pressure is 60 to 120 times as great as at sea level, which would likely make gas bladders inefficient for maintaining buoyancy. Instead, the flesh of the blobfish is primarily a gelatinous mass with a density slightly less than water; this allows the fish to float above the sea floor without expending energy on swimming. Its relative lack of muscle is not a disadvantage as it primarily swallows edible matter that floats in front of it such as deep-ocean crustaceans.

Blobfish are often caught as bycatch in bottom trawling nets. Scientists now fear the blobfish could become an endangered species because of deep-ocean trawling.

Due to its low density flesh, the blobfish's shape is very different when it is out of water. Its unappealing looks have created much discussion in media outlets.

The musician and author Michael Hearst featured a composition titled "Blobfish", inspired by the animal, on his 2012 album Songs For Unusual Creatures, and subsequently created a blobfish episode for his PBS Digital series.

In September 2013 the blobfish was voted the "World's Ugliest Animal", based on photographs of decompressed specimens, and adopted as the mascot of the Ugly Animal Preservation Society, in an initiative "dedicated to raising the profile of some of Mother Nature’s more aesthetically challenged children".

A talking blobfish appears in the film Men in Black 3, sat on the worksurface in the kitchen of the Chinese restaurant along with a couple of other alien food animals, probably suggesting tongue-in-cheek that the blobfish came from space due to their alien appearance.