Turritopsis is a genus of hydrozoans in the family Oceaniidae . According to the World Register of Marine Species, this genus includes the following species: Turritopsis dohrnii ( Weismann, 1883) also known as the " Benjamin Button jellyfish", or the "immortal jellyfish". It can reverse its life cycle and transform itself back to a polyp.

Turritopsis dohrnii are a carnivorous species that commonly feed on zooplankton. Their diet mainly consists of plankton, fish eggs and small mollusks. T. dohrnii ingests food and excretes waste through the mouth. T. dohrnii hunts by using its tentacles as it drifts through the water.