Four-toothed whales or giant beaked whales are beaked whales in the genus Berardius. They include Arnoux's beaked whale (Berardius arnuxii) in cold Southern Hemisphere waters, and Baird's beaked whale (Berardius bairdii) in the cold temperate waters of the North Pacific. A third species, Sato's beaked whale (Berardius minimus), was distinguished from B. bairdii in the 2010s.
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. However, genetic evidence and their wide geographical separation has led them to be classified as separate. Lifespan estimates, based on earwax plug samples, indicate male whales can live up to 85 years, while females can have a lifespan of 54 years. It is estimated that the length at birth is ~4m. Growing up to ~10m, these are the largest whales belonging to the family Ziphiidae. Sato's beaked whale is much smaller, with adult males having a length of ~7m.
While Berardius arnuxii and Berardius bairdii are considered least concern by the IUCN. Berardius minimus is labeled as near threatened as of 2020.
This article currently largely treats four-toothed whales as monospecific, due to a lack of species-specific information.