Arnoux's beaked whale, also called the southern four-toothed whale, southern beaked whale, New Zealand beaked whale, southern giant bottlenose whale and southern porpoise whale is one of the species of Berardius. Arnoux's and Baird's beaked whales are so similar that researchers have debated whether or not they are simply two populations of the same species, until genetic evidence and their wide geographical separation led them to be classified as separate. Little is known about their behavior due to infrequent encounters with live individuals.

The four-toothed whales or giant beaked whales are beaked whales in the genus Berardius. They include Arnoux's beaked whale in cold Southern Hemispheric waters, and Baird's beaked whale in the cold temperate waters of the North Pacific. A third species, Sato's beaked whale, was distinguished from B. bairdii in the 2010s.