The blue whale, Balaenoptera musculus, is likely the largest animal ever to have lived on Earth. Depending on which expert is cited, blue whales once attained lengths of 100 to 120 feet (32 meters) and have weighed up to 160 tons (145 metric tonnes). Blue whales are found throughout the world's oceans. Estimates put their worldwide population at approximately 10% that of prewhaling size, and blue whales are listed as endangered throughout their range.
A huge blue whale swims through the open ocean in this underwater photograph. The blue whale is the largest animal ever to live on Earth.