blue whale, (Balaenoptera musculus), the most massive animal ever to have lived, a species of baleen whale that weighs approximately 150 tons and may attain a length of more than 30 metres (98 feet).

The blue whale (Balaenoptera musculus) is a marine mammal and a baleen whale. Reaching a maximum confirmed length of 29.9 meters (98 ft) and weighing up to 199 tonnes (196 long tons; 219 short tons), it is the largest animal known ever to have existed.

The blue whale (scientific name Balaenoptera musculus) holds the distinction of being the largest known animal ever to have lived on Earth, with individuals reaching up to 100 feet (30 meters) in length and weighing as much as 200 tons. The species is characterized by a mottled bluish-grey body and a broad, flat head.

The blue whale (Balaenoptera musculus) is the largest animal ever known to have lived on Earth. Blue whales are found in all oceans worldwide and are separated into populations from the North Atlantic, North Pacific and Southern Hemisphere.