The only extant species in the genus Orcinus is the orca, Orcinus orca, also called the killer whale.
Although it is commonly called a whale, the orca belongs to Delphinidae, the oceanic dolphin family. It is the largest living member of that family, and its genus also contains fossil species such as Orcinus citoniensis and Orcinus paleorca.
Carl Linnaeus formally described the species in 1758, naming it Delphinus orca before later classifications placed it in Orcinus. The name “killer whale” refers to its reputation as a predator, not to a separate species.
Orcas are highly social apex predators. Different populations may specialize in fish, sharks, rays, seals, dolphins, or other whales, and their hunting methods and vocal traditions can be passed through generations. Some researchers have proposed splitting certain populations into separate species, but the standard classification still recognizes Orcinus orca as the living species of Orcinus.