An omnivore (from Latin omnis = all, vorare = to devour) is an animal that obtains its nutrition by consuming both producers (autotrophs) and other consumers (heterotrophs). In other words, omnivores eat plant matter as well as meat from animals. Most humans are omnivores because we eat fruits, seeds and vegetables, which are from plants, in addition to meat from animals. Other examples of omnivores are some types of bears, which eat fruits, nuts, and leaves of plants, as well as fish and occasionally other animals. In addition, many scavengers, organisms that eat food that they did not kill, are omnivores. For example, crabs, which often scavenge for their food, eat both plant and animal matter.

Because omnivores are not able to make their own food, they are considered heterotrophs. They must obtain all nutrients and energy from the food they consume.

Omnivores hold an important position in food webs of many ecosystems. Unlike producers, which are always at the base of the food web, or herbivores, which only feed on the producers, omnivores can be found at several different levels of a food web. They can be considered primary or first-order consumers because they eat plants. However, they can also be considered secondary and sometimes even third-order consumers because they also eat animals. For example, when a bear eats fruits, nuts, and leaves of a plant, it is a primary consumer. However, this same bear would be considered a secondary or third-order consumer when it eats a fish. Because it is feeding on more than one level of the food web, this bear is considered an omnivore.