Thickest blubber
Balaena mysticetus, Bowhead whale
40 centimetre(s)
Not Applicable ()

The thickest blubber in any animal is possessed by the bowhead whale (Balaena mysticetus), a species of mysticete (aka baleen or toothless) whale native to the Arctic and subarctic marine zones, including those of Russia, Canada and Alaska, USA. Its blubber layer's thickness varies from one body region to another, but at its thickest it is confirmed to attain at least 40 cm (1 ft 3 in), with claims of up to 50 cm (1 ft 7 in) having also been made for this species. The bowhead's closest relatives, the three species of right whale (genus Eubalaena) have also been championed by some researchers for this record, but the majority favour the bowhead (so named, incidentally, because its skull is triangular in shape, like the bow of a ship).

Blubber is only possessed by marine mammals, including cetaceans (whales and dolphins), pinnipeds (seals, sea lions and walruses), and sirenians (sea cows, i.e., manatees and dugongs). Morphologically, blubber consists of vascularized adipose and connective tissue constituting a layer known as the hypodermis, situated directly beneath the true skin's innermost layer, the dermis. Containing more vascularization than normal adipose tissue, its primary functions are thermoregulatory (serving as insulation in cold marine regions) and as fat storage.

Bowhead whales are also the longest-lived mammals with one specimen aged at 211 years old (the median taken from a range between 177 and 245).