Balaenoptera is a genus of rorquals containing eight extant species. Balaenoptera comprises all but two of the extant species in its family ; the genus is currently polyphyletic, with the two aforementioned species being phylogenetically nested within it.

Rorquals are the largest group of baleen whales, comprising the family Balaenopteridae, which contains ten extant species in three genera. They include the largest known animal that has ever lived, the blue whale, which can reach 180 tonnes, and the fin whale, which reaches 120 tonnes ; even the smallest of the group, the northern minke whale, reaches 9 tonnes.