Proteus, a character in the play The Two Gentlemen of Verona by William Shakespeare

Dr. Paul Proteus, the main character in Player Piano by Kurt Vonnegut

Olm (Proteus anguinus), a genus of small cave-dwelling amphibian

Proteus, a genus of trilobites

The plant genus Protea, with the form-multiplicity of its species, was named by Linnaeus after the Greek god Proteus, who could change his form at will.

Proteus, the miniaturized submarine that is injected in a human being's bloodstream in the 1966 movie Fantastic Voyage

Scaled Composites Proteus, an experimental aircraft

Proteus (comics), a Marvel Comics mutant

Proteus IV, a villainous supercomputer in the Dean Koontz novel Demon Seed

Proteus (Steve Jackson game), a board game by Steve Jackson Games

USS Proteus (AS-19), a U.S. Navy submarine tender

Proteus (moon), a natural satellite of Neptune

Proteus syndrome, a very rare congenital disorder known mostly for its most famous sufferer Joseph Merrick (the Elephant Man)

Proteus, a cultivar of Clematis introduced in 1876

Proteus (alchemy), the "first matter" (prima materia), usually the metal mercury

Proteus a prototype wave adaptive modular vessel

Proteus, the Prime Minister in The Apple Cart by George Bernard Shaw

King Proteus, a mythical Greek ruler, featured in the story of Bellerophon

Proteus (instant messaging client), client software for Mac OS X

Proteus of Egypt, an Egyptian king in a version of the story of Helen of Troy

Proteus (film), a film by Canadian director John Greyson

Proteans (body language), a class of subtle body language flirting signals

Proteus (bacterium), a genus of Proteobacteria responsible for many human urinary tract infections.

Protei-5 Russian diver-rider

Proteus (Satellite), a French multimission satellite platform