Biting is a common zoological behavior involving the active, rapid closing of the jaw around an object. This behavior is found in toothed animals such as mammals, reptiles, amphibians and fish, but can also exist in arthropods. Myocytic contraction of the muscles of mastication is responsible for generating the force that initiates the preparatory jaw abduction (opening), then rapidly adducts (closes) the jaw and moves the top and bottom teeth towards each other, resulting in the forceful action of a bite.

Biting is one of the main functions in most macro-organisms' life, providing them the ability to forage, hunt, eat, build, play, fight and protect, and much more. Biting may be a form of physical aggression due to predatory or territorial intentions, but can also be a normal activity of an animal as it eats, carries objects, softens and prepares food for its young, removes ectoparasites or irritating foreign objects (e.g. burred plant seeds) from body surface, scratches itself, and grooms other animals.

Animal bites often result in serious punctures, avulsions, fractures, hemorrhages, infections, envenomation and death. In modern human societies, dog bites are the most common types, with children the most common victims and faces the most common targets. Other species that can exhibit such behavior towards human are typically aggressive urban animals such as feral cats, spiders and snakes, micropredators such as vampire bats and hematophagic arachnids (e.g. mosquitoes, fleas, lice, bedbugs and ticks, whose "bites" are actually a form of sting-like puncture rather than true biting), or dangerous wild carnivores such as wolves, big cats, bears, crocodilians and predatory fishes (e.g. sharks, barracudas and piranhas).