The lion's mane jellyfish, Cyanea capillata, also known as hair jelly, is the largest known species of jellyfish. Its range is confined to cold, boreal waters of the Arctic, northern Atlantic, and northern Pacific Oceans. It is common in the English channel, Irish Sea, North Sea and in western Scandinavian waters south to Kattegat and Øresund. It may also drift in to the south-western part of the Baltic Sea. Similar jellyfish, which may be the same species, are known to inhabit seas near Australia and New Zealand. The largest recorded specimen found, washed up on the shore of Massachusetts Bay in 1870, had a bell with a diameter of 2.3 metres and tentacles 37 m long. Lion's mane jellyfish have been observed below 42°N latitude for some time—specifically in the larger bays of the east coast of the United States.

In Zoo Tycoon

The lion's mane jelly is an adoptable animal in Zoo Tycoon with the expansion pack Zoo Tycoon: Marine Mania. Although it is not labeled as such, it is a show animal. However, it knows only two "tricks": Swim Up and Swim Down.