Blue Whale
The blue whale is a marine mammal
Marine mammal
Marine mammals, which include seals, whales, dolphins, and walruses, form a diverse group of 128 species that rely on the ocean for their existence. They do not represent a distinct biological grouping, but rather are unified by their reliance on the marine environment for feeding. The level of...

 belonging to the suborder of baleen whale
Baleen whale
The Baleen whales, also called whalebone whales or great whales, form the Mysticeti, one of two suborders of the Cetacea . Baleen whales are characterized by having baleen plates for filtering food from water, rather than having teeth. This distinguishes them from the other suborder of cetaceans,...

s (called Mysticeti). At 30 metres (98.4 ft) in length and 180 metric ton or more in weight, it is the largest known animal
Largest organisms
The largest organism found on Earth can be measured using a variety of methods. It could be defined as the largest by volume, mass, height or length. Some organisms group together to form a superorganism, though this cannot truly be classed as one large organism...

 to have ever existed.

Long and slender, the blue whale's body can be various shades of bluish-grey dorsally and somewhat lighter underneath. There are at least three distinct subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...

: B. m. musculus of the North Atlantic and North Pacific, B.