Science & Nature • Marine biology

Phantom jellyfish

The phantom jellyfish, more precisely the giant phantom jellyfish (*Stygiomedusa gigantea*), is a rare deep-sea jellyfish and the only known species in its genus.

By Ethan Anderson| Reviewed by Olivia Bennett, Standards & Fact-Checking Lead| Updated July 26, 2026|2 min read| Fact-checked

The phantom jellyfish, more precisely the giant phantom jellyfish (*Stygiomedusa gigantea*), is a rare deep-sea jellyfish and the only known species in its genus. It is a large, elusive predator found in ocean depths and is reported from most of the world’s oceans except the Arctic Ocean. The species is rarely observed, with only a little over 100 recorded sightings reported in some sources.

Taxonomy

The phantom jellyfish is identified as *Stygiomedusa gigantea*, the sole species in the genus *Stygiomedusa*. It is placed in the family Ulmaridae, which also includes moon jellies.

Distribution and habitat

This species is a deep-sea jellyfish reported from most of the world’s oceans. It is generally associated with great depths in the twilight and midnight zones and is not commonly seen at the surface. Canadian ocean researchers and institutions studying deep-sea biodiversity may encounter or document this species in the North Pacific and other offshore waters.

Appearance and feeding

The jellyfish is known for a large bell and four long, ribbon-like oral arms. These arms are used to capture prey such as plankton and small fish and move it toward the mouth.

Rarity and observations

Phantom jellyfish are seldom observed because they live deep in the ocean and are difficult to study. Reports describe only a limited number of confirmed sightings over more than a century.

Key facts

It is the only known species in the monotypic genus *Stygiomedusa*.
It belongs to the family Ulmaridae.
It is rarely observed, with only a little over 100 recorded sightings reported in some sources.
It can have a bell about 1 metre across and oral arms that can reach about 10 metres long.
Unlike many jellyfish, it uses long oral arms rather than stinging tentacles to capture prey.

🍁

Canadian context

Canadian ocean researchers and institutions studying deep-sea biodiversity may encounter or document rare species like the phantom jellyfish in the North Pacific and other offshore waters.

Frequently asked questions

What is the phantom jellyfish?

It is a common name for the giant phantom jellyfish, *Stygiomedusa gigantea*, a rare deep-sea jellyfish and the only species in its genus.

Where does it live?

It is reported from most of the world’s oceans, typically at great depths, but not from the Arctic Ocean.

What does it eat?

It is believed to feed on plankton and small fish.

How does it catch prey?

It uses four long oral arms to capture prey and guide it toward its mouth rather than relying on stinging tentacles.

Why is it so rarely seen?

It lives in deep ocean habitats that are difficult to access, so encounters with the species are uncommon.

References

Science Focus — https://www.sciencefocus.com/nature/phantom-jellyfish-giant
Supports: Common name, family Ulmaridae, feeding behaviour, and occurrence in multiple oceans.
University of Texas Marine Science Institute — https://utmsi.utexas.edu/science-and-the-sea/radio-program/phantom-giant/
Supports: Scientific name, bell size, deep-sea habitat, and rarity of sightings.
Live Science — https://www.livescience.com/animals/jellyfish/giant-phantom-jelly-the-33-foot-long-ocean-giant-that-has-babies-out-of-its-mouth
Supports: Range, size, and general biology including oral arms and diet.
BBC Newsround — https://www.bbc.co.uk/newsround/59611249
Supports: First discovery history, rarity, and arm length description.
Wikipedia — https://en.wikipedia.org/wiki/Stygiomedusa
Supports: Genus monotypy, family placement, and broad distribution statement.