- Proteus - (Greek mythology) a prophetic god who served Poseidon; was capable of changing his shape at will
--1 is a kind of Greek deity
- Proteus, genus Proteus - type genus of the Proteidae
--2 is a kind of amphibian genus
--2 is a member of Proteidae, family Proteidae
--2 has members: olm, Proteus anguinus - Proteus, genus Proteus - type genus of the Proteidae