Delphinus

The common dolphin (Delphinus delphis) is the most abundant cetacean in the world, with an estimated global population of about six million. It is currently the only member of the genus Delphinus, the type genus of the subfamily Delphininae. This places it as a close relative of the bottlenose dolphin, humpback dolphin, striped dolphin, spinner dolphin, Clymene dolphin, spotted dolphin, Fraser's dolphin, the tucuxi, and the Guiana dolphin.

The common dolphin was once divided into two different species, the short-beaked common dolphin and the long-beaked common dolphin. These are now generally regarded as ecotypes. Recent research shows that many long-beaked populations worldwide are not closely related to one another, often originating from short-beaked ancestors, and they do not consistently share the same derived traits. For this reason, these forms are no longer classified as separate species.