A cuticle, or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection

Various types of "cuticle" are non-homologous, differing in their origin, structure, function, and chemical composition.

the invertebrate cuticle or cuticula is a multi-layered structure outside the epidermis of many invertebrates, notably arthropods and roundworms, in which it forms an exoskeleton.

The main structural component of arthropod cuticle is chitin, a polysaccharide composed of N-acetylglucosamine units, together with proteins and lipids. The proteins and chitin are cross-linked. The rigidity is a function of the types of proteins and the quantity of chitin. It is believed that the epidermal cells produce protein and also monitors the timing and amount of protein to be incorporated into the cuticle.

Often, in the cuticle of arthropods, structural coloration is observed, produced by nanostructures. In the mealworm beetle, Tenebrio molitor, cuticular color may suggest pathogen resistance in that darker individuals are more resistant to pathogens compared to more tan individuals.