The Cyaneidae are a family of true jellyfish.

About 20 species are in this family, including the well-known lion's-mane jellyfish.

The following species are recognized within the family Cyaneidae.

[1] The Cyaneidae species do not possess any internal organs, ganglia, or any other nerve cells.

They do, however, possess gap junctions between neurons which allow for complex reactive behavior and swimming actions.