The species is only a few millimetres wide and scientists say it looks like a flying saucer with a cluster of gonads, or sex organs, on top.
Scientists discovered the jellyfish while surveying the waters outside the CSIRO in Hobart.
The new species has been named Csiromedusa medeopolis, meaning “jellyfish from CSIRO” and “city of gonads”.
Launceston jellyfish expert Lisa-Ann Gershwin says it is an astounding discovery.
“It’s absolutely different from every other jellyfish that’s ever been known,” Dr Gershwin said.
“So we not only put it into its own new species and its own new genus, but it’s actually a brand new family.”
Dr Gershwin says the find is also tremendously exciting.
“Quite possibly and quite humbly the greatest discovery of my career, ever. I mean I’ll be lucky if I ever get a discovery even half as incredible again,” she said.
“You know any mum with a new bub is always excited, but when you have a whole family of new bubs I think it’s triply exciting.”
Dr Gershwin says the jellyfish is harmless to humans.