The killer whale (Orcinus orca), commonly referred to as the orca, and less commonly as the blackfish, is a toothed whale belonging to the oceanic dolphin family. Killer whales are found in all oceans, from the frigid Arctic and Antarctic regions to tropical seas. Killer whales as a species have a diverse diet, although individual populations often specialize in particular types of prey. Some feed exclusively on fish, while others hunt marine mammals such as sea lions, seals, walruses and even large whales. Killer whales are regarded as apex predators, lacking natural predators and preying on even large sharks.

Killer whales are highly social; some populations are composed of matrilineal family groups which are the most stable of any animal species. Their sophisticated hunting techniques and vocal behaviors, which are often specific to a particular group and passed across generations, have been described as manifestations of culture.

The IUCN currently assesses the orca's conservation status as data deficient because of the likelihood that one or more killer whale types are separate species. Some local populations are considered threatened or endangered due to prey depletion, habitat loss, pollution (by PCBs), capture for marine mammal parks, and conflicts with fisheries. In late 2005, the killer whales known as the "southern resident killer whales" were placed on the U.S. Endangered Species list.

Wild killer whales are not considered a threat to humans, although there have been cases of captives killing or injuring their handlers at marine theme parks. Killer whales feature strongly in the mythologies of indigenous cultures.

Noun

killer whale (plural killer whales)

1. A sea mammal related to dolphins and porpoises.
   • 1851 Of this whale, little is known to the Nantucketer, and nothing at all to the professed naturalist. From what I have seen of him at a distance, I should say that he was about the bigness of a grampus. He is very savage - a sort of Feegee fish. He sometimes takes the great Folio whales by the lip and hangs there like a leech until the mighty brute is worried to death. The killer is never hunted. I have never heard what sort of oil he has. Exception might be taken to the name of this whale, on the grounds of its indistinctness. For we are all killers on land and on sea; Bonaparts and sharks included. — Herman Melville: Moby Dick. This ed. 1961 Arnot publishers. p.127.

• Orcinus orca