Which whale species is the largest animal ever known?

The blue whale is the largest animal ever known. Its scientific name is Balaenoptera musculus, and it is a baleen whale in the rorqual family. The largest reliably recorded individuals have reached roughly 30–33 meters, while the heaviest measured specimen weighed about 190 metric tons.

Blue whales became giants partly because their ocean habitat supports enormous seasonal concentrations of krill. They strain vast mouthfuls of seawater through baleen plates, retaining the tiny crustaceans. During feeding season, a blue whale can consume several tons of food in a day.

A common mix-up is the sperm whale, which is the largest toothed whale, not the largest whale overall. Fin whales are also exceptionally long, but they are generally smaller and lighter. Fossil giants such as Perucetus and some ichthyosaurs may have rivalled blue whales, but their size estimates remain debated because they are based on incomplete remains.