• Polymorphism
• Polymorphism (materials science), solids which share chemical composition but are composed of differing crystal lattice forms
• Polymorph (novel), a 1997 novel by Scott Westerfeld
• "Polymorph" (Red Dwarf episode), an episode of the British sci-fi sitcom Red Dwarf
• Polymorphonuclear leukocyte or granulocyte, a type of white blood cell
• An fictional ability in the Warcraft Universe

Polymorph may also refer to:

• Polycaprolactone, in polymer science
• Shapeshifting, in fiction, mythology and fantasy
• Zebra mussel, common name of Dreissena polymorpha