Cheek pouches are pockets on both sides of the head of some mammals between the jaw and the cheek. They can be found on mammals including the platypus, some rodents, and most monkeys, as well as the marsupial koala.

Cheek pouches are located in the thickness of the flange on both sides of the head of some mammals. In some species, such as hamsters, the cheek pouches are remarkably developed; they form two bags ranging from the mouth to the front of the shoulders. Cheek pouches facilitate the rapid collection of food as well as temporary storage and transport of both food and non-food items in several species. Étienne Geoffroy Saint-Hilaire described that some bats of the genus Nycteris have an amazing form of cheek pouches, as they have a narrow opening, through which the bat can introduce air, closing the nasal canal through a special mechanism and pushing air under the skin, so they expire in the tissue, which unites the very loose skin to the underlying muscles. Monkeys of the subfamily of Cercopithecinae make functional use of cheek pouches. The females of some species of hamster are known to hide their young in their cheek pouches to carry them away from danger. Other species of hamsters are known to fill their pouches with air, allowing them to float better while they swim.

Use of cheek pouches for storage is not without risk for the animal. The cheek pouches can become infected as a result of an injury caused by a sharp object inserted into them or a fight. An abscess can form, which can be confused with protuberance with stored food. If the abscess bursts and the pus contained therein is absorbed by the animal, it can develop sepsis and die of the poisonous toxins. Cheek pouches can also become prolapsed.

Hamster cheek pouches have been used as model systems for the study of vascular membranes, healing, and the immune system--notably in the development of abscesses or tumors.

Chipmunks (Tamias) have large cheek pouches that allow them to transport food. The cheek pouches of chipmunks can almost reach the size of their head when full.

Below is the introduction of the legume (pod) of peanut in the cheek pouch of a chipmunk:

One of the classic behavioral characteristics of hamsters (subfamily Cricetinae) is food hoarding. Hamsters carry food to their underground storage chambers using their spacious cheek pouches. A hamster "can literally fill its face with food." When full, the pouches can make the hamsters' heads double, or even triple in size.

The platypus feeds on annelid worms, insect larvae, freshwater shrimps, and yabbies (freshwater crayfish) that it digs out of the riverbed with its snout or catches while swimming. It uses its cheek pouches to carry prey to the surface for eating.