Which cetacean suborder contains the baleen whales?

The cetacean suborder containing the baleen whales is Mysticeti.

Mysticeti is the taxonomic group commonly called the baleen whales or whalebone whales. Its members feed with rows of baleen plates hanging from the upper jaw. Instead of biting prey with teeth, they take in water and strain out organisms such as krill, copepods, and small fish.

Living mysticetes include right whales, bowhead whales, rorquals such as blue and fin whales, gray whales, and the pygmy right whale. The blue whale, the largest known animal, belongs to this group. Modern baleen whales are generally described as a parvorder within Cetacea, although older or simplified classifications may call Mysticeti a suborder.

The main contrasting group is Odontoceti, the toothed whales, which includes dolphins, porpoises, sperm whales, and beaked whales. This distinction makes Pinnipedia and Sirenia unrelated distractors: seals and sea lions are pinnipeds, while manatees and dugongs are sirenians.