Hamsters are generally solitary and primarily nocturnal, although they are sometimes active in the early morning or late evening. They do not climb but are excellent diggers, constructing burrows (burrowing) with one or more entrances and with galleries that are connected to chambers for nesting, food storage, and other activities. They also appropriate tunnels made by other mammals; the striped hairy-footed hamster (P. sungorus), for instance, uses paths and burrows of the pika. Their diet consists mostly of grains but also includes fruit, roots, green parts of plants, invertebrates, and other small animals. Hamsters carry food in their spacious cheek pouches to cache in the burrow. None hibernates during winter, but some experience periods of torpor lasting from a few days to several weeks. Breeding season is from April to October, with two to five litters of 1 to 13 young being born after a gestation period of 13 to 22 days.

Hamsters' northern range extends from central Europe through Siberia, Mongolia, and northern China to Korea. The southern portion of their range stretches from Syria to Pakistan. Throughout dry, open country they inhabit desert borders, vegetated sand dunes, shrubby and rocky foothills and plateaus, river valleys, and mountain steppes; some live among cultivated crops. Geographic distribution varies greatly between species. The common hamster, for example, is found from central Europe to western Siberia and northwestern China, but the golden hamster has been found only near a small town in northwestern Syria.

The 7 genera and 18 species of hamsters form the subfamily Cricetinae of the “true” mouse and rat family Muridae within the order Rodentia (rodent). Their evolutionary history is recorded by 15 extinct fossil genera and extends back 11.2 million to 16.4 million years to the Middle Miocene Epoch in Europe and North Africa; in Asia it extends 6 million to 11 million years. Four of the 7 living genera include extinct species. One extinct hamster of Cricetus, for example, lived in North Africa during the Middle Miocene, but the only extant member of that genus is the common hamster of Eurasia.