The new genus and species Plesiobalaenoptera quarantellii is established and compared to other living and fossil mysticete taxa. The new taxon belongs to the family Balaenopteridae (rorqual and humpback whales) and represents the oldest balaenopterid taxon of the Mediterranean basin coming from Tortonian sediments of the Stirone River, northern Italy (11–7 Ma). Plesiobalaenoptera quarantellii has a wide rostrum, dentary with postcoronoid fossa, periotic with triangular anterior process and raised central portion, tympanic bulla with ventral keel, and high Eustachian opening. From a phylogenetic view, it is closely related to the Late Miocene Parabalaenoptera baulinensis of California, a taxon used to establish the subfamily Parabalaenopterinae. Both Plesiobalaenoptera and Parabalaenoptera are sister taxa of the clade that includes Megaptera, Balaenoptera, and other crown balaenopterids. The presence of the postcoronoid fossa in the dentary of Plesiobalaenoptera quarantellii suggests that the intermittent ram feeding as performed by living balaenopterids was not fully developed in this extinct species.