The North Pacific right whale is a very large, thickset baleen whale species that is extremely rare and endangered. On average and maximum weight, they are the second largest whale species in the world.

Baleen whales, also known as whalebone whales, are marine mammals of the parvorder Mysticeti in the infraorder Cetacea, which use keratinaceous baleen plates in their mouths to sieve planktonic creatures from the water. Mysticeti comprises the families Balaenidae, Balaenopteridae (rorquals), Eschrichtiidae and Cetotheriidae. There are currently 16 species of baleen whales. While cetaceans were historically thought to have descended from mesonychians, molecular evidence instead supports them as a clade of even-toed ungulates (Artiodactyla). Baleen whales split from toothed whales (Odontoceti) around 34 million years ago.