Poisonous Animal, any animal that captures its prey or defends itself by means of a poisonous bite or sting. The term usually is applied to animals whose sting or bite causes death or serious damage, rather than temporary irritation. Thus rattlesnakes and scorpions are considered poisonous animals, but catfish and ants are not. Less commonly, the term is applied to animals whose flesh may cause illness when eaten; examples are sharks and porpoises.

A poison used by an animal for attack or defense is called venom. Most venoms are complex proteins that attack the nervous system or invade the bloodstream. The effect of a venom may vary greatly, depending on the amount injected and the victim's age, weight, physical condition, and degree of natural immunity. Serums called antivenins, obtained from immunized animals, are used to neutralize snake and spider venoms.