Clytia gregaria, sometimes referred to as the gregarious jellyfish, is a small species of hydrozoan in the family Campanulariidae.

Positioned close to the bell margin are four radial canals with a white or yellowish elongated gonad in each.

The mouth opens directly into the manubrium, which has four ruffled lips and is a pale yellow or brownish color.

[1][2] The planula of Clytia gregaria settle on a variety of substrates, on both horizontal and vertical surfaces.

Despite its abundance during the summer, Clytia gregaria is relatively short-lived, and its lifespan rarely exceeds 3 months.