We report on the sighting of a humpback whale Megaptera novaeangliae for the Tyrrhenian Sea, where the species had not been observed previously. Since the 1980s the species has become an increasingly frequent visitor of the Mediterranean Sea, where the mean observation rate is ca. 0.1 subjects/year. The sighting was made on December 10, 2015 at 10 a.m. local time, in the shallow waters of Baia, in the Gulf of Naples (Campania Region, Southern Italy, 40° 49' 0" N, 14° 04' 00" E). The increased sighting frequency of humpback whales suggests that in the near future this species will become more common in the Mediterranean. We remark that Marine Protected Areas might play an important role in protecting the species but appropriate management and effective mitigation of potential threats are essential.