The orca (Orcinus orca), or killer whale, is a toothed whale and the largest member of the oceanic dolphin family. The only extant species in the genus Orcinus, it is recognizable by its black-and-white-patterned body. A cosmopolitan species, it inhabits a wide range of marine environments, from Arctic to Antarctic regions to tropical seas.

Orcas are apex predators with a diverse diet. Individual populations often specialize in particular types of prey, including fish, sharks, rays, and marine mammals such as seals, dolphins, and whales. They are highly social, with some populations forming stable matrilineal family groups (pods). Their sophisticated hunting techniques and vocal behaviors, often unique to specific groups and passed down from generation to generation, are considered to be manifestations of animal culture.

The International Union for Conservation of Nature (IUCN) lists the orca's conservation status as data deficient as multiple orca types may represent distinct species. Some local populations are threatened or endangered due to prey depletion, habitat loss, pollution (by PCBs), captures for marine parks, and conflicts with fisheries. In late 2005, the southern resident orcas were added on the U.S. Endangered Species list.