The blue whale is an enormous baleen whale belonging to the rorqual family (Balaenopteridae). In fact, the blue whale is the largest mammal that ever lived on Earth, with a maximum known size of 34 m and 190 tonnes. The largest specimen found was a female.

It is also the loudest animal on Earth. Its call reaches levels up to 188 decibels. These sounds serve important communication purposes and need to travel long distances since individuals are often separated by hundreds or thousands of kilometres.

The blue whale has a heart that weighs about 450 kg and has 6,400 kg of blood circulating in its body. The heart is about the size of a Volkswagen bug. A small human could crawl through the aorta (the major blood vessel).

Blue whales can dive for 40 minutes and dive to at least 140 m depth. Blue whales are very fast swimmers; they normally swim 5–32 kph but can go up to 38–48 kph in bursts when in danger. Feeding speeds are slower, about 2–6 kph.

Blue whales live at the surface of the ocean and are found in all the oceans of the world.