The Bopyridae are a family of isopod crustaceans in the suborder Cymothoida.

There are 1223 individual species contained in this family.

[1][2] Members of the family are ectoparasites of crabs and shrimp.

They live in the gill cavities or under the carapace where they cause a noticeable swelling.

Fossil crustaceans have occasionally been observed to have a similar characteristic bulge.